chore(docs, build): refactor

TODO:

**Priority**

- [x] Show demos with proper name
- [x] Two sections: Directives & services
- [x] Fix scrollbar on docs app sidemenu
- [ ] Div container for Material movie in the Home page

**Later**

- [ ] Document naming conventions & implicit rules
- [ ] Document the new build tasks & process (revealing pattern in gulpfile w/ comments)
- [ ] Fix view source and edit on github links
- [ ] Show current version SHA on docs home page
- [ ] Add @private