GameObjects no longer fall off plane and (shouldn't) have any collision issues.

I made a copy of the DefaultTrackableEventHandler script for the Cylinder Target and modified it to fit our needs: enabling and disabling the child gameobjects of the Cylinder Target.  If there are any issues let me know and I'll do my best to debug.
Merge pull request #23 from JALsnipe/master

GameObjects no longer fall off plane and (shouldn't) have any collision ...