Adds Causes show route
Adds CausesController files
Updates seeds file to Add causes to petitions
Adds a 'description' column to each cause, and updates annotations for each
Makes description accessible
Overwrites Petition#to_param IOT get 'pretty' URLs
Writes out Cause show view
Places list of causes in Petition index
Places list of causes in Victory index
Updates seed file to create instances of Cause before it tries to create PetitionCauses
Styles causes list in Petition and Victories index