Add represented_formats to application configuration and allow overrides.  By default, represent all formats (old behavior).
Update README to reflect the ability to specify formats to extend/decorate in both the application configuration and in each respond_with call.
Fix build for 3.0 gemfile.  Passes locally for all gemfiles now.
adding ruby 2.0 to travis.
update rake.
Merge branch 'configure-represented-formats' of https://github.com/goldstar/roar-rails
move all decisions into #represents_format?.
rephrasing README, a bit.