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
Skip initial build of site on serve with flag.

Adds --skip-initial-build flag to jekyll-serve, which serves the destination
immediately rather than waiting for the site to be built.

Fixes #1252.
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
Upgrade listen to 2.7.6 <= x < 3.0.0
Merge pull request #2492 from jekyll/upgrade-listen
Update history to reflect merge of #2492 [ci skip]
Try item#to_liquid before looking at the data
Use `raise` instead of logging & aborting
Site: Don't allow the img to be larger than the containing obj. [ci skip]

/cc @penibelst
Remove coverage reporting with Coveralls
Merge pull request #2494 from penibelst/remove-coveralls
Update history to reflect merge of #2494 [ci skip]
Badger badger badger badger [ci skip]
Bump to the latest Liquid version, 2.6.1