Custom JS builder

This adds the custom JS builder to the site.

A link on the "Get the Gear" page has been added to access it.

Also added here is a link to download a zip of the full dev and min versions.  seemed to make more sense to put that here.

What it looks like:

http://blog.lholmquist.org/img/custom.png

What it looks like if nothing is selected:

http://blog.lholmquist.org/img/custom_w_error.png