Rename Item#registration to Item#anchor
Keep support for Item#registration for now as well, since there are some scripts on the mailing list that use it.
Write documentation for Item#anchor.
Make hit-tests work again with projects that don't have a view.

Fixes broken tests.
Use Point.read() for center parameter in Item#rotate
Clean up code and comments in various places.
Include point property in stroke hit-results.
Some minor changes in Satie example.
Merge git://github.com/paperjs/paper.js