Update gh-pages with master changes & create some pages.

This PR update gh-pages branch with latest commits + adds basic index page for root & docs folders, setups jekyll to exclude submodule *markdown files.
Checked this only locally with jekyll 1.5.1, assume gh-pages aren't being generated for fork projects.
![screenshot from 2014-04-27 15 02 57](https://cloud.githubusercontent.com/assets/1506905/2811093/e50e701c-ce03-11e3-81ff-38932e4dde25.png)
Partially related with https://github.com/facebook/react-art/issues/3.