feat(gridster.css): remove possible default pading

Author: vieron

src/jquery.gridster.css

@@ -4,6 +4,7 @@
 
 .gridster > * {
     margin: 0 auto;
+    padding: 0;
     -webkit-transition: height .4s, width .4s;
     -moz-transition: height .4s, width .4s;
     -o-transition: height .4s, width .4s;