Add ability to add conditional comments to not include SVG for IE8 and lower browsers.

[augbog]

SVG isn't supported in IE8 and it would be nice if there was a way I could have it so that my generated SVG sprites would auto-include conditional comments so they aren't included into IE8 pages.

<!--[if (gt IE 8)|!(IE)]><!--><svg>
    ...    
</svg><!--<![endif]-->

Not sure if there is a better route about going about this or if there is a way to customize the template that comes out of grunt-svgstore.