Fix #581 Don't scroll chat automatically if user is not at the bottom

src/static/js/chat.js

@@ -62,9 +62,10 @@ var chat = (function()
     },
     scrollDown: function()
     {
-      if($('#options-scrollchat').is(':checked')){
       if($('#chatbox').css("display") != "none"){
+        if(!self.lastMessage || self.lastMessage.position().top < $('#chattext').height()) {
           $('#chattext').animate({scrollTop: $('#chattext')[0].scrollHeight}, "slow");
+          self.lastMessage = $('#chattext > p').eq(-1);
         }
       }
     },