Do not force developers to use a specific Ruby.

We do not declare a specific Ruby version and/or implementation as the
mainstrea, so if people want to do automatic switching, they're free to use
whatever they want and Hexp should work anyway.
Dynamically detect the DSL methods, closes #17
Take rbx-19mode and jruby-19mode out of the 'allowed to fail' list on Travis. If the build doesn't work for them, that's a bug
Update devtools, in particular Yardstick
Massive cleanup/expansion of the yard docs
Merge pull request #18 from stefanozanella/update_gitignore

Do not force developers to use a specific Ruby.
Don't fail if Yard coverage is higher than the threshold. There seems to be a rounding difference between JRuby and MRI :/
Merge pull request #19 from plexus/yard

Yard