Fixed voting comments bug on Ponder

Summary: When user changed his mind for voting, counting does not work properly. If user vote up first and vote down, vote count must be decreased 2. fixed in javascript file

Test Plan:
http://cihad.phabricator.pompa.la/Q11
user : demo
pass : demodemo

Reviewers: aran, Korvin, epriestley

Reviewed By: epriestley

CC: simsekburak

Differential Revision: https://secure.phabricator.com/D6446