Adds default front-matter support for collecitons
Includes tests for frontmatter defaults in documents
Passes the url to FrontmatterDefaults.all instead of full path
Adds the missing tests for #2405
Adds an example how to use frontmatter defaults with collections
Fixes the extra indentation in cucumber test
Allow usage of different Twitter and Github usernames

and show these links only if twitter-username or github.username are set on _config.yml
Default entries for twitter/github usernames
Badger badger badger badger [ci skip]
Change Github/Twitter keywords to site.{twitter,github}_username
Re: https://github.com/jekyll/jekyll/pull/2485/files#r13525347
Merge pull request #2485 from tomer/patch-2
Update history to reflect merge of #2485 [ci skip]
Bump pygments.rb to 0.6.0.

Closes #2504.
Update history to reflect the closing of #2504. [ci skip]
Merge pull request #2419 from jens-na/collection-defaults
Update history to reflect merge of #2419 [ci skip]
Add includeable module for IO handling.
Begin extracting all IO stuff into Jekyll::IOManager
Split off FS stuff into its own gem.
Move all dangerous FS access calls to the FileSystemAdapter instance.