Implement cookbook following

:fork_and_knife: Implement the ability for users to follow and unfollow a cookbook. Users may click Follow from the cookbook show view and a remote request is sent to `/cookbooks/:id/follow` a 200 response is returned if it is successful. Once the user is following the cookbook they can click Unfollow on the cookbook show view and a remote request is sent to `/cookbooks/:id/unfollow`.

Unauthenticated users are still shown the follow button to entice more people to create community accounts but there is a tooltip that is added to the button that informs them in order to follow they must sign in. When they click the button they are prompted to sign in/up then redirected back to the cookbook they clicked Follow on.