Make all area of the .nav-vertical items clickable

Currently, the .nav-vertical items will only follow the link if the
user clicks directly on the text.  I added this little bit that works
for my case.  Might not work in all cases, but is handy when you have
<a> tags in your <li> tags.
Merge pull request #36 from jameskerr/master

Make all area of the .nav-vertical items clickable