Fix the default group by setting lazily.

Add the first tests.
Add more DSL specs and refactor method signatures.
Add specs for asset DSL method.
I couldn't resist the one liner here.
Put this guy on to travis-ci.
Dry up invalid path exceptions.
Use 1.8 syntax so more people can play.
JRuby 1.8 mode isn't important.

If you have JRuby you have options.
Remove unsupported rubies for green travis-ci.
Merge pull request #38 from craigmcnamara/fix-dsl

Fix issues with the DSL