Clean up demo app and migrate to gh-pages

* Restore Addepar app styles (fixes font and coloring problems)
* Fix usebanner in Gruntfile (no more disappearing headers)
* External links now link to other repos' gh-pages
* Use grunt-release-it instead of release-it
* Update README to point to new docs and describe new release process
* Allow for large hero on overview page
* Separate navigation/footer into their own partial views
* Move some dependencies and clean up build process a bit

@Dylnuge @bigsley 
I'm not a huge fan of this spacing linup style for the exact reason you had to change it (people make changes and then either have to do additional formatting work or accidentally leave it wrong). That said, it's not actually a problem, and if we're going to use it it's of course best that it's right