rename count field to direction for votes and add cancel vote form

migration change column
rename vote count to vote direction in vote model
fix forms and controller to work with direction field name
add cancel vote form that resets vote direction to 0
add voting to answers

add forms for each answer (vote up, cancel vote, vote down)
refactor votes_controller to use params[:commentable_type],
so that controller code is reusable and doesn't hard-code in
the commentable_type and vote#create is usable for questions and
answers
remove db/development.sqlite so gitignore works properly
move Vote#create logic into Vote model method

refactor to move controller logic into the model
pass in params and the current_user.id
Merge pull request #11 from rwarbelow/voting_part_2

WIP: Add voting for Answers