added the acts_as_votable gem

and made pin act_as_votable, and user act_as_voter
also added a like button on the index page as well as on the show page, which also displays the number of votes
make sure that the one who edits or deletes a pin is the owner

removed the buttons from the ui if you're not the author
added server side validation to check if the current user is the author of a pin before edit,update or delete