new look github page

Lots of new javascript and css to create the theme we wanted.
@mwernimont can you filter two things on the repos: 1) is their language R (this way the splash HTML repos don't show up) and 2) does the repo have a description? (This way the barebones packages don't show up)

@ldecicco-USGS thoughts? This page is the public facing set of R repos, so should we use a filter?