Re-implement reactDirective to be more angular-oriented

With reference to issue #10, this PR has the following goals:

- Re-implement `reactDirective` to accept a React component instead of an injectable name as its first parameter
- Re-implement `reactComponent` to use `reactDirective`

This PR contains **breaking changes** to the current usage of `reactDirective`. It also requires AngularJS 1.3+

**TODO:**

- [x] `reactDirective` should accept a React component as its first parameter
- [x] `reactDirective` should sanity check its parameters
- [x] `reactDirective` should update the view when changes in the angular models occurs
- [x] `reactComponent` should be implemented using `reactDirective`
- [ ] ~~React components rendered via `reactDirective` should have the means to update angular models when updating React props~~