homepage changes

1) Put documentation links in a "Documentation" menu in the nav bar 
2) Put New Pubs and Browse links in a "Explore" menu in the nav bar
3) Pub Twitter widget is on the right and the New Pubs of the USGS is below the search.
4) Made the links in New Publications of the USGS (both the heading link and the titles) underline on hover
5) Ignored the advanced search task because Jim said to