Added hooks into topic follow and unfollow

src/topics/follow.js

@@ -12,6 +12,7 @@ var notifications = require('../notifications');
 var privileges = require('../privileges');
 var meta = require('../meta');
 var emailer = require('../emailer');
+var plugins = require('../plugins');
 
 module.exports = function(Topics) {
 
@@ -56,6 +57,7 @@ module.exports = function(Topics) {
 					return next(new Error('[[error:no-topic]]'));
 				}
 				db.setAdd('tid:' + tid + ':followers', uid, next);
+				plugins.fireHook('action:topic.follow', {uid : uid, tid : tid});
 			},
 			function(next) {
 				db.sortedSetAdd('uid:' + uid + ':followed_tids', Date.now(), tid, next);
@@ -74,6 +76,7 @@ module.exports = function(Topics) {
 					return next(new Error('[[error:no-topic]]'));
 				}
 				db.setRemove('tid:' + tid + ':followers', uid, next);
+				plugins.fireHook('action:topic.unfollow', {uid : uid, tid : tid});
 			},
 			function(next) {
 				db.sortedSetRemove('uid:' + uid + ':followed_tids', tid, next);