RFR Email user

You can actually wrap this into your first test, "user successfully uploads a review":

```ruby
scenario 'user successfully uploads a review' do
  # existing setup for test...
  ActionMailer::Base.deliveries = []
  prev_count = UserReviewConfirmation.deliveries.count

  # existing expectations...
    expect(UserReviewConfirmation.deliveries.count).to eq(prev_count + 1)
    expect(ActionMailer::Base.deliveries.size).to eq(1)

    last_email = ActionMailer::Base.deliveries.last
    expect(last_email).to have_subject("Caleb has reviewed the coffee shop you added!")
    expect(last_email).to deliver_to(user.email)
end
```