Switching over to RequireJS for tests.

This *removes* all my crazy asynchrony hacks, and replaces it with the official Karma RequireJS support.

In addition, this will let me easily:

* Have FS agnostic tests (e.g. buffer tests); right now these run once for every file system
* Have FS specific tests (subfolder for each file system)
* Have FS extension modules that add factory methods for testing purposes (e.g. adds BrowserFS.FileSystem.<name>.getTestInstantiations(cb)).
* Use TypeScript for the test harness and support code (!!).
* Pull in arbitrary BFS internal components in tests.

Fun!