Dynamic filter of result-set to map

[kieppie]

Automagically filter results when zooming, moving map

[kieppie]

related to #14

[kinow]

I've done it in the past with Google Maps and GMapEZ. If I recall correctly, there was a callback in the GMapEZ JS library called whenever the map changed. So we just need to query the server again for the specific locations. I can't build the project right now (see #25) but will give it a try and maybe submit a pull request int he next days/weeks.