Setup Spinner class as React component, implement spinner into login

Here's my first stab at implementing the Flux pattern in the app. I've used `login.coffee` as my guinea pig...all I'm trying to do is show a Spinner at the start of a `ServerRequest`, and hide it when one of the `done/error` events methods are fired.

It looks like it works, but I'd just like to make sure I'm doing it all correctly. I'm not entirely sure that I'm accessing the `store` properly in the `login` view.

Thanks.
you're going to need to emit a `change` event here. Because `@requestEventChange(false)` is called after the `done` callback, `isLoading` will still be false after the `setLoginData` change event fires.

This also bring up the question whether it is cleaner and more efficient to just set `isLoading` to `false` right in the `setLoginData` data method, since you know at that point the request has completed.