Set up navbar (wincent.dev, 6b3cfb4)

In 2.0 spirit we're going for the simplest navigation possible. Some of the CSS exhibits some mysterious behaviour (namely, I had to set a -0.35em left margin on the links in the list items in order to get the highlighting to correctly extend all the way to the preceding border; I have no idea why this hack was required) but it displays correctly in both Firefox and Safari.

Signed-off-by: Greg Hurrell <greg@hurrell.net>