TOC improvements

1) Highlight current file in the dropdown
2) Make dropdown expand also from keyboard
3) Display links in TOC as block so they get 100% width

Ad 1, I've made it with inline javascript at the end of the file but this is rather a hack, would be better to do this in jade at build time, but my eyes bleed when I read that (and yes, I'm a noob :P)
So, before integrating, should be checked if this doesn't break IE etc., or to rewrite it as a build-time thing.