Add whitespace
Bump to Mercenary ~> 0.3.0

https://github.com/jekyll/mercenary/releases/tag/v0.3.0
Bump Mercenary to ~> 0.3.1
Remove unnecessary references to `self`
Merge pull request #2090 from coreyward/selfish
Update history to reflect merge of #2090 [ci skip]
Merge pull request #2085 from jekyll/mercenary-0-3-0
Update history to reflect merge of #2085 [ci skip]
Merge pull request #2084 from nslater/add-whitespace
Update history to reflect merge of #2084 [ci skip]