Correct TOUCH_DOWN behaviour in TouchHandler

if a TOUCH_DOWN event triggers a open scene, then the TOUCH_UP will be missed by the touch handler instance. This will cause the next TOUCH_DOWN to call an old touchProps[e.idx]. TOUCH_DOWN should never need to call a touchProps[e.idx]
Merge pull request #59 from halfnelson/master

Fixes a small bug in Flower.TouchHandler