add PyCarolinas Iterators and Generators Talk

I wanted to put it on the site because it's one of my favorite talks,
but I had to dig the slides and whatnot out of my Dropbox and put them
on GitHub first.
fix hover behavior in navbar

When expanding the border on the navbar links to 2px, I forgot to
correspondingly update the padding-left, so hovering over a link
shifted it a bit. This commit removes that, and also removes turning
the links bold when hovered over.