Moved control points into the pipe.
Added play/pause and speed control.
Merge remote-tracking branch 'origin/master'
#118, #104 Use CanvasNode to render the water drops.  The performance on iPad2 improves to 35-40 fps on safari and about 25fps on chrome. It used to be 5-7 fps previously.
#134 Raise the lower drag bound of the sensors by 50px