Added a cooldown period of 500 seconds before sending new socket events for vote and rating
Changed from topidId --> _id to use the db field that hase index by default on the opinion model
Added a section about setting the server ulimit
Started using emitSingle(Voting/Rating)GraphUpdate that only emits event to the calling socket. This means that we don't send an update to ALL of the users in the "room" when a new user wants the graphs for the first time.
Fixed missing room argument to the emitRatingGraphUpdate & emitVotingGraphUpdate
Added error handeling in the emitRatingGraphUpdate & emitVotingGraphUpdate