Get out of sys.modules

I've been frustrated with Python's global variables recently but it's
not until I read Armin Ronacher's essay [1] that I decided that Cosmic
should not have any global state at all. Turns out it's done quite
simply and elegantly with Werkzeug's Context Locals [2]. The way you
can use them via a `with` statement makes them feel like a language
feature, which they indeed should be.

[1] http://lucumr.pocoo.org/2009/7/24/singletons-and-their-problems-in-python/
[2] http://werkzeug.pocoo.org/docs/local/