fix(gridster): Removing previously added style tags before adding new one.

Hopefully fixes #211 and #294.

dist/jquery.gridster.js

@@ -3592,6 +3592,8 @@
                 (x * opts.widget_base_dimensions[0] +
                 (x - 1) * (opts.widget_margins[0] * 2)) + 'px; }\n');
         }
+	
+	this.remove_style_tags();
 
         return this.add_style_tag(styles);
     };

src/jquery.gridster.js

@@ -2795,6 +2795,8 @@
                 (x - 1) * (opts.widget_margins[0] * 2)) + 'px; }\n');
         }
 
+        this.remove_style_tags();
+
         return this.add_style_tag(styles);
     };