Add 'html5mode' option, some customizations

I added an option for html5Mode, which defaults to true.  If false, it will make all the docs links be hash-links.  This enables me to host the docs on gh-pages.

I also removed everything which links back to http://docs.angularjs.org.

Another thing I want to add is an obvious "github" link on the navbar, and share/star buttons (similar to lots of projects, eg http://angular-ui.github.io/bootstrap).

Perhaps just a customizable header/footer as well would be cool.

To try it out, just put 'ajoslin/grunt-ngdocs' as a dependency in package.json.