Add X and Y axis rotation

Adds `rotateX` and `rotateY` methods to `Point`, `Path` and `Shape`

I've added a test case, and added animation support to the test suite so that the test case can demonstrate rotational animation along the three axes.

Possible alternative to jdan/isomer#36 ?

![isomer-rotation](https://cloud.githubusercontent.com/assets/181548/3791191/83e8f3b2-1b2d-11e4-9a01-b69272998b7a.gif)