* Provide example for s3_host_name

Gives an example, since not everyone knows the format required.

* Shorten line per Hound comment

* Added convert_options and source_file_options documentation to the Post Processing README section

* made minor markdown changes

* Add migration_version variable to migration generator for rails 5 compatibility

* Update syntax to satisfy hound

* Ruby 2.4.0 compatibility (doen't use Fixnum anymore)

* Fix typo

* Use Integer instead of 0.class

* Updated the Readme, added a submit button to the form and made some notes to make instructions more clear

Use consistent code style in README examples

Update README.md

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