Week2

This is my work up to lesson 12 in week 2. I've flown solo for a lot of this, and still haven't watched some of the solutions, so there is plenty to review.
This also feels like it should move to the model.You can create a method in the video model:
```ruby
def average_rating
  reviews.average(:rating).round(1) if reviews.average(:rating)
end
```
Then in the `video/show` template you can do `@video.average_rating`