Pass a notification path when a user follows another

When a user followed another, a notification is created, but with
no path, so on plugins like pushbullet, it would default to trying
to build a topic url, but the required values were null, leading to
a broken url.

src/socket.io/user.js

@@ -310,7 +310,8 @@ SocketUser.follow = function(socket, data, callback) {
 			notifications.create({
 				bodyShort: '[[notifications:user_started_following_you, ' + userData.username + ']]',
 				nid: 'follow:' + data.uid + ':uid:' + socket.uid,
-				from: socket.uid
+				from: socket.uid,
+				path: '/user/' + userData.userslug
 			}, next);
 		},
 		function(notification, next) {