Refactor duplicate code to function: redrawRuler
Added checking so not to adding rulers and windows resize event again if plugin is called multiple times, now you can call plugin several times to enable/disble crosshair/mouse pos :
Added a "method" to draw grids, (as we can now call the plugin multiple times already)
e.g.:
$('body').ruler({
     drawGrid:{ top: 120, left: 550, width: 100, height: 200, background: '#fff000' }
});

note: background is optional
Added some text to the grid
Fix the position of grids by counting the Ruler sizes
Updates Readme