In other parts of the codebase, "filename" refers to the part after the
directory path it is contained in. e.g. `original_filename` in
attachment.rb.

This makes this file easier to read by conveying the range of arguments
ContentTypeDetector.new accepts.

Prioritize MimeMagic over the `file` binary for content type detection
when it finds a match. Fall back to `file` if MimeMagic can't match
anything.

`file` incorrectly detects Open Office XML files (e.g., xlsx, docx) as
zip since they're implemented as zipped archives of xml files. MimeMagic
detects them properly.

The `aws-sdk` development dependency was updated to `~> 1.6` in #1816
to resolve issues with the creation of 0-byte files on S3 (see #1729).
However, there is no runtime dependency on `aws-sdk`, and the
documentation still suggests that users install an earlier version of
`aws-sdk` that produces the problems in the referenced issue.

This commit updates the docs to recommend the use of `aws-sdk` `~> 1.6`
with Paperclip.

* Uses Paperclip's Tempfile instead of Ruby's in Thumbnail
* Also includes a test for TempfileFactory to be sure it does not revert to similar behavior
* In the tests, give the OS some wiggle room in the Tempfile name to ensure the error does not occur before we are ready for it. The wiggle room is needed because the randomized part of the name has a variable number of characters.

Rescue only `NotIdentifiedByImageMagickError` in
`Attachment#post_process_style`. Other errors should bubble up, because
they are meaningless for the end-user, but important for the programmer.

Fixes #1352.

It's useless because there is the same conditional in https://github.com/thoughtbot/paperclip/blob/master/lib/paperclip/railtie.rb#L25, and if ActiveRecord is not defined, Glue will not run.

The reason behind this I'm trying to use StringioAdapter inside the mailer, and it fails because `length` used in one of the `mail` gem:
https://github.com/mikel/mail/blob/master/lib/mail/message.rb#L1997

Also you can see that normally `size` has `length` alias, for example in a `StringIO` class:
http://ruby-doc.org/stdlib-1.9.3/libdoc/stringio/rdoc/StringIO.html#method-i-length

Let me know, if this change requires test case, I will add it.

As referenced in #1739

Just because the `Rails` constant is defined, it doesn't mean we're
actually in a Rails app. Since there are people who use Paperclip
outside of Rails, and there's no reason we shouldn't be able to run in
those situations. This commit checks for `Rails.env` instead of just
checking for `Rails` and assuming `Rails.env` works.

This reverts commit 06802254.

@see https://github.com/thoughtbot/paperclip/commit/804b4edc1d8d7ca9865170e34f26da7d66f6d0d5#commitcomment-8497017

Including + now.

Many people have complained that the Media Type Spoof Detection does not
work properly for their files. While whitelisting is available for some
files, it's not a general solution. This option leaves the "secure by
default" of the media checker in place, but allows people to turn it off
completely if they so choose.

Column-specific options can be specified by using its name,
for example:

```
t.attachment :avatar, created_at: { index: true }
```

Use proper name for zh-TW locale.

Use proper name for zh-CN locale

Add explicit unlink to intermediate files from processors.

Also, add integration tests for custom processor definition and unit
test for Paperclip.load_processor (thoughtbot/paperclip#1535).

... instead of `lib` of `lib/paperclip_processors`.
Fixes thoughtbot/paperclip#1534