Refactored Layout and View, upgraded to latest LM

The Layout object was a simple wrapper over the Layout constructor
instead of extending the constructor itself.  I've patched this to make
it more consistent and removed duplicative methods.  I've also removed
the tests for `removeView` since that is now a built-in method.

The latest LM contains bugfixes and render performance updates that
unforuntately have to be opt-out.  Areas in the source or tests that are
expecting synchronous renders must be patched to work asynchronously to
take advantage.
Same, the rationale is outlined here:

https://github.com/tbranyen/backbone.layoutmanager/pull/421