#169 Unit test for CurrentUserStore.

Will probably need to test more extensively, but it ensures that getCurrentUser is returning the correct user.
By not mocking a bunch of these, you're turning this into more of an integration test than a unit test. Integration tests are important, but that's not what this task is about.

You'll want to keep the Dispatcher and CurrentUserActions mocked. To test that the Store responds correctly to events emitted by the Dispatcher, you can simulate the Dispatcher calling the callback. `Dispatcher.register.calls` is an array of calls to `Dispatcher.register`, where each call is an array of arguments. In this case, the callback is the first argument of the first (and only) call, so in `beforeEach` you can do:
```javascript
// You'll need `var registerCallback;` above
registerCallback = Dispatcher.register.mock.calls[0][0];
```

Then, now that you have a reference to the callback, you can test login/logout with:
```javascript
registerCallback({actionType: ...});
expect(...);
```