Bounding box method for arcTo method, plus demo and test

ArcTo is some crazy :shit:. Sometimes, geometry makes me dizzy.

![http://uploads.hipchat.com/10819/141831/q3sw7sbbb84e793/Screen%20Shot%202013-02-19%20at%202.11.32%20PM.png](http://uploads.hipchat.com/10819/141831/q3sw7sbbb84e793/Screen%20Shot%202013-02-19%20at%202.11.32%20PM.png)

Thankful for the good people of the internet: http://www.dbp-consulting.com/tutorials/canvas/CanvasArcTo.html