Bump Jekyll to v2.3.0

https://github.com/jekyll/jekyll/releases/tag/v2.3.0
https://github.com/jekyll/jekyll/compare/v2.2.0...v2.3.0

@benbalter, this should solve some support tickets.
Bump jekyll-redirect-from to 0.6.0
Merge pull request #88 from parkr/redirect-from-bump

Bump jekyll-redirect-from to 0.6.0
:gem: bump to 23
Merge pull request #87 from parkr/jekyll230

Bump Jekyll to v2.3.0
:gem: bump to v24
bump sitemap :gem: to 0.6.0
Merge pull request #89 from github/sitemap-0-6-0

Bump sitemap :gem: to 0.6.0
:gem: bump to v25
Bump to jekyll-redirect-from v0.6.1

https://github.com/jekyll/jekyll-redirect-from/releases/tag/v0.6.1
Bump to Jekyll 2.4.0

Release: https://github.com/jekyll/jekyll/releases/tag/v2.4.0
Diff: https://github.com/jekyll/jekyll/compare/v2.3.0...v2.4.0 (all the important stuff is in lib/)
Co-sponsored by @gjtorikian and @kansaichris who put a LOT of work into this.

With love from SF.
Merge pull request #90 from parkr/redirect-from-0-6-1

Bump to jekyll-redirect-from v0.6.2
:gem: bump to v26
Actually bump jekyll-redirect-from to 0.6.2
Merge pull request #92 from github/actually-bump-to-062

Actually bump jekyll-redirect-from to 0.6.2
:gem: bump to v27
Merge pull request #91 from parkr/jekyll-2-4

Bump to Jekyll 2.4.0
:gem: bump to 28
convert to mercenary
default branch