Clean up demo app and migrate to gh-pages

  * 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
  * Move some dependencies and clean up build process a bit

@Dylnuge @bigsley