Working on refactoring the extend() method, breaking it down into separate methods.
Add some doc comments to private methods.
Build updates:

* Wrap source file in UMD block from Gruntfile.
* Run tests using Jasmine from Gruntfile.
* Add LICENSE file
Refactor Class.js into separate files for Utility methods and the actual building of classes
Move documentation building to 'grunt-jsduck' task, and remove local executable.