Test against Ruby 2.2.0 on Travis CI
Merge pull request #1389 from tricknotes/ruby-2.2

Test against Ruby 2.2.0 on Travis CI
Use HTTPS by default in new project Gemfiles. Closes #1372
Add 3.3.6 changes to Changelog
Merge pull request #1391 from natebird/patch-1

Add 3.3.6 changes to Changelog
Add tests for inline minification in PHP files, correct typos.
Prevent side-effects of content type testing.
Use configurable content type for detection of minifiable content.

  - Allows minification of arbitrarily proxied resources.
  - Uses a locally-defined MIME type to detect PHP files.
Use Oga for detection of inline stylesheets.
Remove extra '//' from HTML fallback comments.
Use Oga for detection of inline JavaScripts.