Fixed Website Link in README.md

Changed "http://codeforamerica..org/brigade" to "http://codeforamerica.org/brigade."
The broken link was really bugging me :P
Merge pull request #28 from cyrieu/patch-1

Fixed Website Link in README.md
Fixed Links in Navbar

The links in the nav.html file had broken paths (tools and about); I fixed them so that they go to the correct pages