Rails 4 Support and Travis Integration

Make changes to make the gem Rails 4 compatible.

i) Removed ActiveResource reference.  
ii) Updated gemspec to allow Rails 4.
iii) Moved alias_method_chain to the ActionView::Helpers::AssetTagHelper module.  
iv) Changed the name of the spec controller to be Rails 4 compatible.  
v) Removed deprecation warnings in specs.  
vi) Updated Rakefile to include spec task and make it the default.
vii) Added a .travis.yml file