added tap gesture recognizer to Set card collection view
made cards that have been matched hidden from view
background of selected Set cards is now gray
removed unneeded files
added methods to remove cards and return the number of cards in play to support removal of matched cards from play
deleted old code to decorate card buttons
deleted old code to decorate buttons; removed hiding of unplayable cards because cards are now removed from the model after a match
removed old code for decorating card buttons; added code to remove matched cards from the model and the collection view
took out logging message in removeCardAtIndex
removed logging during init
removed unneeded files from the project
syncing README