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.

Cocaine changes how it returns the supplied path in 0.5.5. While this
has no effect on the workings of Paperclip in a normal capacity, it does
break the tests. This change fixes that and updates the cocaine
dependency to 0.5.5.

Turns out that between fog 1.22.0 and fog 1.25.0, there was a change to
how fog builds S3 expiring URLs. This changes to test to be the common
point between the two versions. All we need to do here is make sure that
the expiring URL is being constructed.

In the process, this also updates all the appraisal-generated
Gemfiles.

Also, in the process, this meant I had to take away the builder version
restriction. This was put in so that `bundle`ing wouldn't take forever,
but I'm unsire whether this needed to happen with this version or if
builder just needed to be separate from the Gemfile. I'm commimtting
this and asking the people who reported the problem. If you don't see a
revet commit, everything was fine.

This reverts commit ae3ec237.

This reverts commit 8d70c198.

This reverts commit 8e0eb4ce.

During the fixing of the previous commit, the tests broken. Turns out
that between fog 1.22.0 and fog 1.25.0, there was a change to how fog
builds S3 expiring URLs. This changes to test to be the common point
between the two versions. All we need to do here is make sure that the
expiring URL is being constructed.

In the process, this also updates all the appraisal-generated Gemfiles.

Also, in the process, this meant I had to take away the builder version
restriction. This was put in so that `bundle`ing wouldn't take forever,
but I'm unsire whether this needed to happen with this version or if
builder just needed to be separate from the Gemfile. I'm commimtting
this and asking the people who reported the problem. If you don't see a
revet commit, everything was fine.

```
 paperclip $ rspec spec/paperclip/integration_spec.rb --profile 1
Testing against version 4.1.7
.........................[deprecated] I18n.enforce_available_locales will default to true in the future. If you really want to skip validation of your locale you can set I18n.enforce_available_locales = false to avoid this message.
.........

Finished in 15.19 seconds (files took 0.60155 seconds to load)
34 examples, 0 failures

Top 1 slowest examples (9.54 seconds, 62.8% of total time):
  Paperclip Many models at once does not exceed the open file limit
    9.54 seconds ./spec/paperclip/integration_spec.rb:18
```

to

```
 paperclip $ rspec spec/paperclip/integration_spec.rb --profile 1
Testing against version 4.1.7
.........................[deprecated] I18n.enforce_available_locales will default to true in the future. If you really want to skip validation of your locale you can set I18n.enforce_available_locales = false to avoid this message.
.........

Finished in 10.95 seconds (files took 0.59585 seconds to load)
34 examples, 0 failures

Top 1 slowest examples (5.33 seconds, 48.7% of total time):
  Paperclip Many models at once does not exceed the open file limit
    5.33 seconds ./spec/paperclip/integration_spec.rb:18
```

at trim indent

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

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 }
```

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

File.exists? has been deprecated since Ruby 1.9.2

Fixes #1550

* `fog_spec.rb:328` fails intermittently due to a race condition
* Use [TimeCop][1] gem to freeze time during the spec
* Extract magic number
* Break long line

[1]: https://github.com/travisjeffery/timecop

![TimeCop
Poster](http://www.deconstructingmovies.com/wp-content/uploads/2014/03/timecop-poster.jpg)