Feature parse config files with erb

Also made few other changes, you can lookup change log. 

Basically I've added proper test suite, refactored it a bit, and placed everything under module. Added to_hash method and parsing yaml files with ERB before loading config.

Last thing to mention, I removed some dependencies like rails and rspec-rails - it will load engine only if it's a rails app. So you can also use it within other apps like sinatra, padrino and plain old ruby ;)