Updating OSX packaging script

-Adding a shell script to build a distributable app for OSX.
-Updating py2app script to use icon, set title etc.
-Removing build generated files from repo and ignoring in .gitignore.
-Couple of minor issues on OSX.
--multiprocessing.Queue.qwait isn't implemented for some unix platforms, so using multiprocessing.Queue.empty instead.
--use correct path on OSX to load images.
Adding distributable app for OSX