Allows `s3_host_alias` to be set to CDNs which support S3 Bucket prefix.

[fixes #2287]

Bug introduced in 1c7d7f66

Per https://github.com/thoughtbot/paperclip/commit/1c7d7f66ceea27cfe604e3a13c2eb87df217d13a#commitcomment-18765681 request

Rebased #2120 to master.
Paperclip duplicates the original files quite a lot as part of its validation process. (#1642, #1326).
When uploading large files (several hundred megabytes to gigabyte range), this becomes a problem: The web server will be busy creating 3 - 4 duplicates on disk, while the app (and potentially the user) are waiting for the upload operation to complete.
This pull request introduces hard links instead of ```FileUtil.cp``` where possible to keep the logic as-is but save time and disk space.

[Amazon S3 Transfer
Acceleration](http://docs.aws.amazon.com/AmazonS3/latest/dev/transfer-acceleration.html)
enables fast, easy, and secure transfers of files over long distances
between your client and an S3 bucket. And
[aws-sdk](https://github.com/aws/aws-sdk-ruby) has allowed us to enable
this feature in version 2.3.0 (more detail is
[here](https://github.com/aws/aws-sdk-ruby/pull/1163)).

You can now pass a configuration option (:use_accelerate_endpoint) when
config Paperclip with S3. You can enable the [Amazon S3 Transfer
Acceleration](http://docs.aws.amazon.com/AmazonS3/latest/dev/transfer-acceleration.html)
by set this option:
```:use_accelerate_endpoint => true```

[fixes #2291]

* correct S3 specs to use the correct keys in the s3_credentials hash
* S3 tests work with a region that requires s3_domain_url

[fixes #1985]

Adapters now accept an options parameter, that currently specifies
the type of hash digest to use.  The default value remains MD5, but
can be specified to be any OpenSSL-supported digest.  The specs are
modified to reflect that.

The task just reassigns all of the attachments, thereby regenerating
their fingerprints.

* ignore invalid content-disposition header

[fixes #2283]

Fix typo.

Progress on https://github.com/thoughtbot/paperclip/issues/2071.

[closes #2282]

[ci skip]

[closes #2155]

Adds a Code Climate configuration enabling Fixme, Rubocop, and
Duplication.

The Code Climate RuboCop engine uses a newer version of RuboCop than the
current Hound config, so .hound.yml was modified to work for both. The
only notable change was removing PreferredHashMethods because there is
no syntax for that cop that works with bout Hound and Code Climate.

[ci skip]

Update NEWS file.

[ci skip]

* Add default `content_type_detector` to `UploadedFileAdapter`

[fixes #1314]
[ci skip]

Default `s3_protocol` used to be `http` when `:s3_permissions` are
`:public_read` (default), and `https` when `:s3_permissions` are
anything else.

With an empty String as default, if the page is served over HTTPS,
attachment URL will be HTTPS, and if the page is served over HTTP,
attachment url will be HTTP.

`public-read` is an authorization concept, independent form the
encryption of the HTTP connection used to read the file. As such, the
one shouldn't define the other.

[fixes #2038]

If `only_process` list is not empty, but it doesn't contain `:original`
style, original file hasn't been reprocessed and it's not needed to
rewrite/reupload it.

[fixes #1993]
[fixes #2046]
[fixes #1804]

Documentation update for thoughtbot/paperclip#2217.

[These lines](https://github.com/thoughtbot/paperclip/blob/95acf3b898bd782f4429d42fd2d8812505390328/lib/paperclip/storage/s3.rb#L101-L112) in the documentation indicated that the value for the `s3_storage_class` configuration option should be `:reduced_redundancy`. However, using this value with Paperclip 5.0.0 results in a `Aws::S3::Errors::InvalidStorageClass` error with the message `The storage class you specified is not valid`.

The [documentation for the `Aws::S3::Object#storage_class` method](http://docs.aws.amazon.com/sdkforruby/api/Aws/S3/Object.html#storage_class-instance_method) in the `aws-sdk` gem documentation indicates that the correct value is now `REDUCED_REDUNDANCY` (along with a few other potential values).

There's a subtle difference between what `\Z` and `\z` consider the "end
of string" which is that the uppercase version allows a single trailing
newline:

```
/\Afoo\Z/.match("foo\n")

/\Afoo\Z/.match("foo\n\n")

/\Afoo\z/.match("foo\n")
```

* There is no need to pass options argument to UrlGenerator
* Houndci compliance

I recently implemented a custom processor that used the Exifr gem to
extract EXIF information from images uploaded to a Paperclip attachment.
Exifr's processor uses readbyte to parse the EXIF header, so it hit
errors when Paperclip's File-like object didn't have one. There's also a
test for this delegation.

I've also tidied up the README documentation for custom processors,
hopefully to be more clear than before. There was some duplicated
content between the "Post Processing" section and the "Custom Attachment
Processing" section, and those sections were separated in the file. I've
dedicated the "Post Processing" section to Paperclip's built in
thumbnailing processors, and made "Custom Attachment Processing" section
solely about writing & using your own custom processors. This should be
a more understandable progression, as built-in functionality is
discussed first & separately from extending Paperclip.k

- The uri io adapter now seeks for the content-disposition header
  if this is pressent the value filename is taken instead of the
  last path segment for the resource file name
- Fix style comments
- Applied the Tute Costa refactor to URI Adapter.
- Added entry to  the NEWS file.
- Removed editor tracking file
- Fix test cases

Before this change, the value for `preserve_files` was the string `"true"`, potentially confusing users that they should use stringified booleans like `"true"` and `"false"`.

However `"false"` would evaluate as truthy, and preserve files.
This appears to have been a factor in https://github.com/thoughtbot/paperclip/issues/1445#issuecomment-51430186

AWS no longer accepts `:aes256` as an encryption value and will raise
`Aws::S3::Errors::InvalidArgument` with the message `The encryption method
specified is not supported`. It should instead be `"AES256"`.

This commit makes no implementation change, but for those that use
source code and tests as documentation, it should help prevent
confusion.

Release v5.0.0

Update NEWS file.

[ci skip]

* Add `read_timeout` option to `UriAdapter#download_content` method
* Default `read_timeout` is `nil`
* Update NEWS

* replaced if-not-blank with if-present

an instance of code was testing presence via `!a.blank?`. this is now
replaced with a more readable version: `a.present?`

* replaced 2 if-not-blank checks with if-present checks

* temporarily restrict travis

* reverted travis changes

* readded whitespace

Add test to prevent regression regarding excessive logging

Fix a nil error in failure_message of content type validation matcher

[ci skip]

When a matcher uses both `allowing` and `rejecting`, and validation fails,
`@missing_rejected_types` might still be `nil`.

When a matcher only uses either of the two, a part of the message is `nil`.

Note: this is most likely not the way we want to test our matchers, but it
demonstrates the current issue.