Hiding the action button if they're not signed in.

This might want to be updated to let them know they
get more functionality if they sign in..
Showing a message to the user if they're not signed in.

Better to show that actions are possible
Basics of deleting working, still a very nasty transition
Checks for 401 status and signs out user if their token has changed
Merge branch 'signout_if_token_changed' into new_delete
Signing out user on delete with bad token
Updating endpoint to use staging server
Don't perform segue, just pop the view controller and return
Adding NSNotificationCenter for alerting about deleted carpool
Showing an alert rather than using an action sheet
Adding completion block for telling user message was sent
Updated project to recommended settings for Xcode 5.1
Merge pull request #5 from snowpool/signing_out_bad_user

Adding delete functionality and clearing bad token.