Like button

[sophiecollard]

Acceptance criteria

Given a Tweet
Then I can see the like count for that Tweet

Given a Tweet I have not liked
When I click the like button
Then the button state changes to "liked"
And the like count is incremented by 1

Given a Tweet I have liked
When I click the like button
Then the button state changes to "not liked"
And the like count is decremented by 1

Implementation phases

1. Show like count for each Tweet
2. Show an authenticated user whether they have liked the Tweet they are viewing
3. Allow authenticated user to like/unlike a Tweet