Fix link to license.
Add dat.gui.js

dat.gui.js will be used to create settings menu in dev mode.
Fix index page

Unnecessary elements was removed.  dat.gui.js was added to the head into
library section.
Add dat.gui support in the game.

Settings gui should now be switchable via menu button. Event for the `h`
(code: 72) keydown was removed from the dat.gui.js. It should be also
removed for all future updates of this library.