fix(gridster): wrong addition solved in add_faux_rows/cols by adding parseInt

Closes ducksboard#426, ducksboard#425

Author: rept

src/jquery.gridster.js

@@ -2963,7 +2963,7 @@
     */
     fn.add_faux_rows = function(rows) {
         var actual_rows = this.rows;
-        var max_rows = actual_rows + (rows || 1);
+        var max_rows = actual_rows + parseInt(rows || 1, 10);
 
         for (var r = max_rows; r > actual_rows; r--) {
             for (var c = this.cols; c >= 1; c--) {
@@ -2989,7 +2989,7 @@
     */
     fn.add_faux_cols = function(cols) {
         var actual_cols = this.cols;
-        var max_cols = actual_cols + (cols || 1);
+        var max_cols = actual_cols + parseInt(cols || 1, 10);
         max_cols = Math.min(max_cols, this.options.max_cols);
 
         for (var c = actual_cols + 1; c <= max_cols; c++) {