Add change_picture handler and notice.

Server-side handler for picture changing, and
add the notice about picture changing for users.

server/classes.js

@@ -125,6 +125,7 @@ module.exports = {
             _.each(this.users, function(user) {
                 user.socket.emit('picture_changed', {pid: picture._id, width: picture.width, height: picture.height});
             });
+            this.notice('Picture has been changed to '+picture._id);
         };
     }
 };

server/socket.js

@@ -58,6 +58,16 @@ function Socket(web) {
             user.say(data.msg);
         });
 
+        socket.on('change_picture', function(data) {
+            if(channels[data.channel]) {
+                PictureModel.findOne({_id: data.pid}, function(err, picture) {
+                    if(picture !== null) {
+                        channels[data.channel].changePicture(picture);
+                    }
+                });
+            }
+        });
+
         socket.on('change_nick', function(data) {
             if(!user) {
                 socket.emit('error', {type: 'NoUser'});