Co-author: Ned Batchelder <ned@edx.org>

By transparently proxying between the XModuleDescriptor and the XModule,
and between their runtimes, we can make them act as a single class, so
that we can swap in an actual XBlock instead.

Update existing tests and provide new ones to test new paradigm.

Refactor new set_many and update XBlock version number.

Added self to authors.

Conflicts:
	AUTHORS
	CHANGELOG.rst

Without accessing .pk, it's possible for the user object to still be a
SimpleLazyObject, which breaks Django's query engine

http://stackoverflow.com/questions/11875737/django-filtering-drafts-by-user-causes-error

Use the XBlock library as the base for XModule, so that we can incrementally rely on more and more of the XBlock api