Update Raphael, gRaphael and Colorwheel

The first commit in this branch updates the Raphael library to version 2.1.0, the gRaphael library to version 0.5.1 and also the colorwheel. The second commit makes changes to the stats widget to work with the new Raphael API.

Besides from fixing the stats widget, it doesn't seem that there are more changes required. I tested the following things:
* The neuron staging area makes use of the colorwheel. It works like expected with the newer colorwheel version.
* Neuron tracing seems to work as well. I can draw, move, join and delete nodes and connectors. Arrows to synapses can be created and removed.
* The compartment graph widgets seems to draw things correctly, as well.

Is there anything I forgot to test? Anyway, it would be best if someone with a more expertise for the tracing tool than me could test this, too.