added fingerprint check

MeatBunches currently allows for the same person to post 8 different gifs, but that's hardly faithful to the Brady Bunch and also doesn't reflect the true character of Meatspace.  Therefore, I added a bit of code to client.js to ensure that each cube will be filled by a new meat. i.e. Created a fingerprints array, and push each new fingerprint to the array, return if the fingerprint already belongs to the array.