Switch Pygments to Rouge and update Gemfile.lock.
Add JRuby to Travis builds.
Revert "Add JRuby to Travis builds."

Ah, right, Redcarpet...

This reverts commit f31715708e369c4ecb41cafa6f06178ad15e8008.
Update CHANGELOG.
Merge pull request #34 from aprescott/rouge

Switch to using Rouge over Pygments