notification changes

-only send a notification when the person you follow creates a topic
-you still get a notification per post if you are following a topic
-changed notifications.push so that it sends the notifications over a
period of time, currently to 50 users per second
-optimized topics.notifyFollowers and
user.notifications.sendTopicNotification, they no longer query the
database for the topic and post data instead they get it as params
-you can no longer follow yourself :)
-changed mongo sortedSetRemove so that it doesn't use $in if there is
only a single value to remove

src/database/mongo/sorted.js

@@ -61,18 +61,21 @@ module.exports = function(db, module) {
 	};
 
 	module.sortedSetRemove = function(key, value, callback) {
+		function done(err) {
+			callback(err);
+		}
 		callback = callback || helpers.noop;
 		if (!key) {
 			return callback();
 		}
-		if (!Array.isArray(value)) {
-			value = [value];
-		}
-		value = value.map(helpers.valueToString);
 
-		db.collection('objects').remove({_key: key, value: {$in: value}}, function(err) {
-			callback(err);
-		});
+		if (Array.isArray(value)) {
+			value = value.map(helpers.valueToString);
+			db.collection('objects').remove({_key: key, value: {$in: value}}, done);
+		} else {
+			value = helpers.valueToString(value);
+			db.collection('objects').remove({_key: key, value: value}, done);
+		}
 	};
 
 	module.sortedSetsRemove = function(keys, value, callback) {