late night optimizations

-isMemberOfSets returns true/false instead of 1/0
-when loading the posts of a topic only get the userdata for each user
once, before this commit if a topic had 10 posts from 2 different users
we were getting the user data for each user 5 times (drunk)
-getVoteStatusByPostIDs and getFavouritesByPostIDs no longer make
pids.length calls to the db, they use isMemberOfSets now
-getUserInfoForPost renamed to getUserInfoForPosts and doesnt make
uids.length calls to db, uses getMultipleUserFields instead

src/topics/unread.js

@@ -45,7 +45,7 @@ module.exports = function(Topics) {
 						return callback(err);
 					}
 					var newtids = tids.filter(function(tid, index, self) {
-						return parseInt(read[index], 10) === 0;
+						return !read[index];
 					});
 
 					async.filter(newtids, function(tid, next) {