Modifying header snippet to allow tracking script at bottom of page & adding Facebook sharer.php tracking

Two parts here:

1) It is no longer necessary to include the full BSD tracking script in the middle of the GA snippet, which means you can technically put the snippet in the header and the tracking script in the footer with the rest of your javascript.

2) Since Facebook seems to be moving more to having people use their sharer.php method of sharing content, I've added an onmousedown event that fires when someone clicks those links. Since there is no javascript callback to attach to with these events, it simply checks for the click.

Opinions/corrections/other viewpoints encouraged.

Thanks