Update .gitignore

was using advice from this: (Jan 13)
http://fixbyproximity.com/2013/01/git-unity-3d-source-control/
and this (June 11)
http://www.chrisdanielson.com/2011/06/04/unity3d-projects-version-control-git/

Updated to this: (Feb 13)
http://www.dannygoodayle.com/2013/02/14/using-unity-with-git/