Use yajl since it is already a dependency

Both JSON and Yajl were listed as dependencies. Pygments.rb already requires yajl, so let's just use that instead of using both.
Merge remote-tracking branch 'origin/master' into just-yajl

* origin/master: (42 commits)
  its always greener
  that new green shell
  Removing stale extension
  Update README.md
  Add moon interpreter for MoonScript
  Bumping version for 3.4.1 release
  Use text.html.erb scope for HTML+ERB files
  Add sample .dyalog file for file type APL
  Added extra Papyrus sample files.
  Add sample Papyrus script
  Add Papyrus support
  Add LOLCODE support
  Add ProGuard config files to vendored files
  Recognise *.dyalog as APL sources
  Assign a bunch more TextMate scopes
  CI step for samples
  Add .command as a Shell file extension
  CI config
  Vendored gems
  Update cibuild
  ...

Conflicts:
	Rakefile
Merge pull request #1608 from github/just-yajl

Use yajl since it is already a dependency