Merge pull request #53 from dyxliang/master

Fixed back button issues of going to incorrect screens.
Merge pull request #11 from ZooTypers/master

updating with davids change for back button
home screen pause and back button pause now all works
Merge pull request #54 from winglam/master

home screen pause and back button pause now all works for singleplayer
Merge pull request #13 from ZooTypers/master

Getting updates.