Week2

week 2 mid-week code review
Thanks Brandon for pointing out the direction, I did it :) not using persisted? though, here's what I did [commit](https://github.com/j1wu/myflix/commit/b5a975fb3453af85e91b4951b1f0d4ea9d286931), I tried to accomplish this the TDD way, the feature is there and working, but the test is not...
this test won't pass
```
        it 'persists review content if no rating' do
          post :create, review: {rating: '', content: 'keep this!'}, video_id: seven.id
          expect(response.body).to include('keep this!')
        end
```
The rspec [doc](https://www.relishapp.com/rspec/rspec-rails/docs/request-specs/request-spec) says there's a `response.body` method, but it came back ""