gridster/fix: using comparators in sort methods.

Sort method by default orders alphabetically, but we are sorting numbers
and this means that: 40 < 6. And we not expect this result.

src/jquery.gridster.js

@@ -1384,7 +1384,9 @@
                 return true; //break
             }
 
-            upper_rows[tcol].sort();
+            upper_rows[tcol].sort(function(a, b) {
+                return a - b;
+            });
         });
 
         if (!result) { return false; }
@@ -1439,7 +1441,9 @@
                 return true; //break
             }
 
-            upper_rows[tcol].sort();
+            upper_rows[tcol].sort(function(a, b) {
+                return a - b;
+            });
         });
 
         if (!result) { return false; }