changes to index and layout

I modified the main page that shows up at
  http://clawpack.github.io/doc/index.html

(eventually www.clawpack.org will point to this page?)

Also changed where some of the links on the top menu point, and added a condensed table of contents (in PR #22).

Clawpack points to index
Docs points to condensed toc.

Does this look ok for now?