Can be run with `node_modules/.bin/jest` for now; didn't want to disturb the grunt setup.
Right now one test fails with:
```
FAIL browser/ui/__tests__/ReactDOMComponent-test.js (1.423s)
● ReactDOMComponent › updateDOM › it should update styles when mutating style object
- Expected: '0' toEqual: '0.5'
at Spec.<anonymous> (src/browser/ui/__tests__/ReactDOMComponent-test.js:99:33)
```
which I can only assume is a jsdom problem -- no other asserts fail.