Pairing with @kitop

Update NEWS.

[fixes #2134]
[ci skip]

Add Rails master appraisals in preparation for Rails 5

While working on this branch, Kito found that this test fails due to:

https://github.com/rails/rails/commit/6ec8ba16d85d5feaccb993c9756c1edcbbf0ba13#diff-fdcf8b65b5fb954372c6fe1ddf284c78R76

We are not yet sure if it's a bug in paperclip or in Rails itself. With
current `ActiveModel::Errors` implementation the following happens:

```
record.errors # => @messages = {}
record.errors.include?(:foo) # => false
record.errors # => @messages = { :foo => [] }
```

Which bit us in:
https://github.com/thoughtbot/paperclip/blob/69f18375333234b6f395300266e2612936bd242e/lib/paperclip/validators/attachment_file_name_validator.rb#L23

Another related Rails commit:
https://github.com/rails/rails/commit/b97035df64f5b2f912425c4a7fcb6e6bb3ddab8d

I worked around the issue by changing what we assert in this spec. I am
still not sure that this is a bug in current Rails master.

cc @kitop for review

Ref: https://github.com/rails/rails/commit/481e49c64f790e46f4aff3ed539ed227d2eb46cb

`silence_stream` was deprecated in Rails 4.2 and removed in Rails 5
because it was not thread safe. Paperclip is not running the tests in
threaded mode, it's safe to add the method back in a test support
module.

Ref: https://github.com/rails/rails/commit/2386daabe7f8c979b453010dc0de3e1f6bbf859d

Specifically:

> Chains of callbacks defined **with** a `:terminator` option will
> maintain their existing behavior of halting as soon as a `before_`
> callback matches the terminator's expectation. For instance,
> ActiveModel's callbacks will still halt the chain when a `before_`
> callback returns `false`.

In terminator callbacks, the `result` value changed to be a lambda now.
This change reflects that, updating the terminator to compare the result
of the block to `false`.

Also:

* Removes Rails 4.1 branch (we don't support it anymore)
* Rewrite for legibility: change `unless` for `if`

`bundle exec rails -v` was taking seconds every time, making the test
suite run very slow. This changes the code to compare the version
against `ActiveRecord::VERSION`, which is going to be the same one as
`rails -v`, making it much, much faster.

Simplifies condition: we no longer support Rails < 4.2, so we test for
`>= "5.0"` or fallback to `4.2` branch.

- Also bump Travis Ruby 2.2.x version to 2.2.4

We found that uploading large files to S3 would result in a socket error
("connection reset by peer") occasionally and lately much more
consistently. In researching this I saw that many people got this error
when uploading too large of a file without multipart chunking. I would
have assumed fog did this automatically but the default chunk size may
be too high. In order to address this I wanted to drop the chunk size to
100MB.

Rather than hard-code this I opted to expose a `fog_option`
configuration option that lets me pass any additional options I want to
the fog's `#create` call. This is similar to the `fog_attributes` option
implemented in CarrierWave which [addresses the same
problem](http://stackoverflow.com/a/11867978/201911).

We've been running this now for a week in production and it seems to
resolve the issue.

https://github.com/thoughtbot/paperclip/pull/2135

Related with https://github.com/thoughtbot/paperclip/issues/2122

[ci skip]

See https://www.ruby-lang.org/en/news/2016/02/24/support-plan-of-ruby-2-0-0-and-2-1/

Remove attr_protected related specs (was removed in rails 4)

Skip calculating fingerprint when it is not used

The MD5 sum of an attachment is only necessary if the model has a corresponding
_fingerprint column. If this column is absent, there is no need to calculate the
MD5, which can be an expensive operation for large files.

Accomplish this by deferring the fingerprint calculation using a block. If the
_fingerprint column is absent, the block is never called, and the calculation
is avoided.

Modify the Gemfile for testing with mime-types 3

-   Also modify the appraisals to be more flexibly specified.
-   The specs are '>= 1.16' and '< 4.0' because the major versions of
    mime-types have steadily restricted the supported versions of Ruby at a
    different rate than Rails. The Appraisal for Rails 5 can be specified as
    either '>= 2.0, '< 4.0' or '~> 3.0' depending on how other gems restrict
    mime-types versions.

    -   mime-types 1.x supports any version of Ruby, but no longer receives any
        updates (it hit EOL on 27 October 2015).
    -   mime-types 2.x supports Ruby >= 1.9.2, but will only receive security
        and data updates until 21 November 2017.
    -   mime-types 3.x supports Ruby >= 2.0 and is the active development
        version of mime-types.

-   The APIs that paperclip uses are compatible between all three versions of
    mime-types.

Relax mimemagic version constraint to ~> 0.3.0

Updated copyright notices to 2016 [ci skip]

Remove unused vars `column_(type|options)` from `remove_attachment` method

Replace File.exists? with File.exist? in paperclip.gemspec

File.exists? is deprecated and produces unecessary warning.

These variables were introduced in:
https://github.com/thoughtbot/paperclip/commit/6ea7c26512434a
but their usage were canceled in:
https://github.com/thoughtbot/paperclip/commit/c740fb171fe

Remove AWS v1 support

TODO: Simpify lib/paperclip/storage/s3.rb

See:

* https://github.com/thoughtbot/paperclip/issues/2049

Removes Rails 3.2 and 4.1 support

In preparation for Rails 5, which, when it is released, will make Rails
3.2 and 4.1 unsupported.

See:

* http://weblog.rubyonrails.org/2015/12/18/Rails-5-0-beta1/
* https://github.com/thoughtbot/paperclip/issues/2049

Remove locales from main repository

Extract another repository only concerned with locales:
https://github.com/thoughtbot/paperclip-i18n

A user of paperclip might choose to add `paperclip-i18n` as a dependency
for their application, or copy over the related locale file into their
project.

This is a first step in splitting some parts of the codebase into other
projects. Simple and relevant contributions like new translations might
get lost in the shuffle of dozens of PRs awaiting for approval, that
take time to review and merge.

Locales are a simple enough problem to be handled in an external
repository, where tests for consistency across translations run in less
than a second, and PRs can almost trivially be merged in.

Fix condition to include Schema, using 'ActiveRecord::Base' instead o…

Remove duplication by reusing existing method.

See https://github.com/thoughtbot/paperclip/issues/1974

[closes #2064]

v4.3.2 is a different tree than `master`, which is now targeting v5.
Thank you both for this commit and merge, but I'll revert it: paperclip
v4.3.2 doesn't include AWS v2 support.

This reverts commit 9b33fc0a.

[ci skip]

Update README with version requirement for aws-sdk