tell ruby what the filename of markups.rb is
defer loading of markups gems until they're first used
add :eager option to markup
eager load markdown implementations for fallback
refactor command/gem details into implementation classes
add special cased markdown implementation
fix GitHub::Markup.preload!
cache file extension regexp instead of recompiling it every time
add a markups accessor method for @@markups
Merge pull request #231 from github/lazy-load-markups

Lazy load markup gems