Move vendor prefixed properties before the unprefixed ones.
Use the shorthand font property when possible.

Conflicts:
	site/_includes/css/style.css
Be explicit with the `background` property.
Remove units from zero.
Remove duplicate properties.
Add fallback colors.
Add missing vendor prefixed properties.
Simplify selectors.
Add document.output to list of liquid vars in output.

CLoses #2232.
Change Travis extension
Change Fury extension
Change Gemnasium extension
Switch to 2.1
Fix typo in documentation
Remove literal lang name from class, fix #2284

If code language is C classes for comment and language are the same
Merge pull request #2291 from chezou/fix-typo-in-docs
Update history to reflect merge of #2291 [ci skip]
Update tests

Remove language literal from class in test/test_redcarpet.rb
Switch 2.1 to 2.1.1
Merge pull request #2290 from penibelst/travis-workaround