Literally Canvas 0.5.2

[Steve Johnson]

I wrapped up the React dependency fix into 0.5.1, and then merged some good PRs and did 0.5.2.

v0.5.2
* Reset undo stack when loadSnapshot is called, fixing a memory leak
* Moving shapes with the selection tool is on the undo stack

v0.5.1:
* Fixes for React dependency
* Undo support for moving selected shapes