RFR Cp delete vote

issue #11 
These shouldn't be instance variables (not in a `before :each` block :) )

I'd probably add a test here to make sure that the "Delete Vote" link doesn't appear if the user hasn't voted.

You could also dry up this spec by creating a factory for votes:

```ruby
factory :vote do
  user
  review
  direction "up"
end
```
Then in your specs:

```ruby
  scenario "delete vote" do
    vote = FactoryGirl.create(:vote)
    bus = review.ride.bus
    sign_in_as(vote.user)

    visit bus_path(bus)
    within("#review-#{vote.review.id}") do
      expect { click_link "Delete Vote" }.to change(Vote, :count).by(-1)
    end
  end
```