fix(gridster): fixed expand_widget bug not expanding full width of window

fix(gridster): user can specify size_x when expanding widget

Author: floyd_hawkes

src/jquery.gridster.js

@@ -499,15 +499,15 @@
      * @method expand_widget
      * @param {HTMLElement} $widget The jQuery wrapped HTMLElement
      *  representing the widget.
+     * @param {Number} size_x The number of cols that will occupy the widget.
      * @param {Number} size_y The number of rows that will occupy the widget.
      * @param {Function} [callback] Function executed when the widget is removed.
      * @return {HTMLElement} Returns $widget.
      */
-    fn.expand_widget = function($widget, size_y, callback) {
+    fn.expand_widget = function($widget, size_x, size_y, callback) {
       var wgd = $widget.coords().grid;
-      var max_size_x = Math.floor(($(window).width() - this.options.widget_margins[0] * 2) /
-          (this.min_widget_width + this.options.widget_margins[0] * 2));
-      var size_x = Math.min(max_size_x, this.cols);
+      var max_size_x = Math.floor(($(window).width() - this.options.widget_margins[0] * 2) / this.min_widget_width);
+      size_x =  size_x || Math.min(max_size_x, this.cols);
       size_y || (size_y = wgd.size_y);
 
       var old_size_y = wgd.size_y;