disable input "keydown" on smartphones - it's redundant there (no tab key), breaks input editing, and has some impact on performance

fix #138

code/chat.js

@@ -606,6 +606,7 @@ window.chat.setupTime = function() {
 
 
 window.chat.setupPosting = function() {
+  if (!isSmartphone()) {
     $('#chatinput input').keydown(function(event) {
       try {
         var kc = (event.keyCode ? event.keyCode : event.which);
@@ -621,6 +622,7 @@ window.chat.setupPosting = function() {
         debug.printStackTrace();
       }
     });
+  }
 
   $('#chatinput').submit(function(event) {
     event.preventDefault();