Fix Homebrew hyperlink on README

Rename FactoryGirl to FactoryBot

[ci skip]

This is a year in the making, with a security patch motivating it.

[ci skip]

Remove the URI adapters. Few people use them by default and they can
allow insight into the internal networks of the server. If you want to
enable them, add (for example) `Paperclip.DataUriAdapter.register` to
your `config/initializers/paperclip.rb` file.

This is related to CVE-2017-0889.

Elsewhere fix CI: it's `s3.us-west-2` now, with a dot.

FactoryGirl is a factory bot now

Exception is the root of Ruby's exception hierarchy, so when you rescue Exception you rescue from everything, including subclasses such as SyntaxError, LoadError, and Interrupt etc which is a bad idea.

Fix: rescue from StandardError.

Some of the titles were inconsistent in capitalization.

Fixes the following warning shown by JRuby 9.1.6.0:

> gems/paperclip-5.1.0/lib/paperclip/storage/filesystem.rb:49: warning: `&' after local variable or literal is interpreted as binary operator even though it seems like argument prefix

Fix Travis CI

Thanks for the tip, @brendon!
https://github.com/thoughtbot/paperclip/pull/2331#issuecomment-262910522

Otherwise cucumber doesn't load development dependencies.

- Updates cucumber (https://github.com/cucumber/gherkin2/issues/320#issuecomment-139572490)
- Removes `bundle exec` from commands ran in cucumber steps
- Simplifies framework_major_version (we can assume it always is 4 or
  higher)
- Inline unneeded methods
- Fix some Ruby warnings

* Remove old Tempfile tests from Thumbnail spec
* Move Tempfile tests to tempfile_spec.rb

Fix typo in README

s3_permissions can no longer be a symbol. Must be a string.
Providing a string causes hard to debug errors in AWS.

[fixes #1943]

header was changed recently (https://github.com/thoughtbot/paperclip/commit/5202acbf4b642230bef71a8dd534bcca11fb4373#diff-04c6e90faac2675aa89e2176d2eec7d8L740), but link was not and now it's broken

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.