Update Rails integration to account for changed method name.  Minor change to shoulda integration.
added initialization section to README to show how to specify the length of the unique_key
Merge pull request #24 from petergoldstein/feature/update_rails_4_compatibility

Rails 4.0.6 / 4.1.2 compatibility
Merge pull request #26 from msquitieri/add_initialization_to_readme

added initialization section to README to show how to specify the length of the unique_key
bump version
Go to root_url if shortened url isn't found