show all locations of a traveller on one map

Implementation for #10

![screen shot 2014-03-30 at 20 04 23](https://cloud.githubusercontent.com/assets/615777/2562027/ecaa0b76-b835-11e3-8588-4c164a62997f.png)

I've now got the maps working with geo-coding on the fly by adding some delays between the requests.

Tested in current versions of Safari, Chrome and Firefox on OSX.