Develop better demo application

The demo app is in https://github.com/rochacbruno/Flask-GoogleMaps/tree/master/examples

Accessible in: http://flaskgooglemaps.pythonanywhere.com

The page currently is very simple and needs improvements.
- [ ] Better layout (simple, yet beautiful) (example: https://jz6.github.io/PoGoMap/ )
- [ ] A menu bar to handle project links (repo, chat, issues etc)
- [ ] mobile enabled (responsive)
- [ ] split the demo into different views (one per map with links in menu bar)
- [ ] Put better code example below each map, with (html + python) tabs and code highlight (maybe using embedded gist)
- [ ] A section "who uses fgmaps" including https://github.com/AHAAAAAAA/PokemonGo-Map
- [ ] Include Flask-Caching in demo app views

Start by reviewing the demo application in the examples/ directory and comparing it with the deployed demo at flaskgooglemaps.pythonanywhere.com. Break the requested redesign into separately scoped changes, then verify the relevant checklist items: responsive layout, navigation, separate map views, improved code examples, the users section, and Flask-Caching integration.

Written by the indexing model from the issue text.