change grid line width

Closes #2

LGTM given by: @scottmatthewman

Squashed commit of the following:

commit 432c34bd8fa91827324019800978812231b9f5be
Author: Tonmoy Saikia <tonmoy.saikia@talentica.com>
Date:   Tue Jun 17 19:55:11 2014 +0530

    change grid line width