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

Fix merge problem with S3 storage

Includes memory usage adjustments.

Conflicts:
	lib/paperclip/storage/s3.rb

Cache interpolator methods and reduce memory allocations - rebased on v4.3

something in aruba 0.10.x is breaking the cucumber specs

Inspected by https://github.com/dkhamsing/frankenstein

[ci skip]

Resolve broken CI tests due to upstream gem changes

something in aruba 0.10.x is breaking the cucumber specs

the name string is used multiple times in interpolation so storing it reduces object creation

this commit primarily uses frozen strings to reduce object creation during interpolation.
the :basename method now uses File.basename(file, ".*") rather than a Regexp. basename may be called multiple times.

by using the attachment name (symbol) and Class as keys we reduce the number of Strings created before hitting the cache