Focus not handled correctly

[rbenson]

If you use only a keyboard, the focus is not correctly handled. If we use http://projects.jga.me/toc/, and tab to download, pressing enter, then tab again brings focus back to the TOC link at the top. If focus was properly handled, pressing tab after enter should place focus on the "production" link. To properly move focus tabindex="-1" must be added to the heading it is jumping to, or the <span> that this plug in creates before the heading.