Run tests in random order
Start to convert the heroku Rake task to a heroku:set Thor task

Pending tests.

[ci skip]
Add the thor gem dependency

Rails 3 depends on Thor ~> 0.14.0 which requires Thor's "option" method
to be replaced with the older "method_option" alternative.
Remove Rails-specific Rake tasks
Remove the runtime dependency on Bundler
Don't depend on ActiveSupport::StringInquirer in the tests
Reconfigure Travis to build only master and to use Bundler