Fix the responsive grid to be able to shrink.

demos/responsive.html

@@ -21,7 +21,7 @@
                     enabled: true
                 }
             }).data('gridster');
-            $('.gridster  ul').css({'width': $(window).width()});
+            $('.gridster  ul').css({'padding': '0'});
         });
     </script>
 </head>

src/jquery.gridster.js

@@ -3689,7 +3689,7 @@
 	 */
 	fn.get_responsive_col_width = function () {
 		var cols = this.cols || this.options.max_cols;
-		return (this.$el[0].scrollWidth - ((cols + 1) * this.options.widget_margins[0])) / cols;
+		return (this.$el[0].clientWidth - 3 - ((cols + 1) * this.options.widget_margins[0])) / cols;
 	};
 
 	/**