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.js

@@ -270,6 +270,9 @@ var async = require('async'),
 			}
 
 			async.parallel({
+				mainPost: function(next) {
+					Topics.getMainPost(tid, uid, next);
+				},
 				posts: function(next) {
 					Topics.getTopicPosts(tid, set, start, end, uid, reverse, next);
 				},
@@ -284,26 +287,6 @@ var async = require('async'),
 				},
 				tags: function(next) {
 					Topics.getTopicTagsObjects(tid, next);
-				},
-				mainPost: function(next) {
-					Topics.getTopicField(tid, 'mainPid', function(err, mainPid) {
-						if (err) {
-							return next(err);
-						}
-						if (!parseInt(mainPid, 10)) {
-							return next(null, []);
-						}
-						posts.getPostsByPids([mainPid], function(err, postData) {
-							if (err) {
-								return next(err);
-							}
-							if (!Array.isArray(postData) || !postData[0]) {
-								return next(null, []);
-							}
-							postData[0].index = 0;
-							Topics.addPostData(postData, uid, next);
-						});
-					});
 				}
 			}, function(err, results) {
 				if (err) {
@@ -325,6 +308,27 @@ var async = require('async'),
 		});
 	};
 
+	Topics.getMainPost = function(tid, uid, callback) {
+		Topics.getTopicField(tid, 'mainPid', function(err, mainPid) {
+			if (err) {
+				return callback(err);
+			}
+			if (!parseInt(mainPid, 10)) {
+				return callback(null, []);
+			}
+			posts.getPostsByPids([mainPid], function(err, postData) {
+				if (err) {
+					return callback(err);
+				}
+				if (!Array.isArray(postData) || !postData[0]) {
+					return callback(null, []);
+				}
+				postData[0].index = 0;
+				Topics.addPostData(postData, uid, callback);
+			});
+		});
+	};
+
 	Topics.getTeasers = function(tids, callback) {
 
 		if(!Array.isArray(tids)) {