Added validates statements to the appopriate models
Added support to detect user name based on downcase (case insensitive) and to prevent multiple users from having the same name
Added uniqueness validation to name field of user table ro prevent duplicate user names
Implemented for login page, added return_errors method for the user model, added validation that guesses for each card are not blank.
Limited username chars to letters, numbers, underscores.
Users can now delete cards from a deck
Users can delete cards and decks, as well as seeing all of the cards in a deck