Migrate tests to Mocha

The name says it all. High order bits:

  - I'm not using proxyquire because its `@global` feature mucks with the node.js module cache & fundamentally breaks React, which expects to only be loaded once.
  - We apply the JSX transformer to anything with an `@jsx` in it. I tried renaming all our components to `.jsx`, but this made node-inspector less pleasant.
  - It's still helpful to mock out BioDalliance and the AttributeCharts. I did this via the preprocessor and a global list of React Components to mock. Mocks are now opt-in.
  - Since we're no longer using Jasmine, I switched to `sinon` for stubs and `assert` for tests. We can use something fancier like `chai` if you prefer.

Tests run a lot faster now, and hopefully less flakily!

Fixes #128 
Hmm, so we purposely didn't do it this way before; any reason we need an API change for these mocha tests?