Map does not center on available locations when first viewed

[almereyda]

In #46 we have found out, that the map sometimes does not immediately show the available locations instantaneously.

This is due to the original map extend being focused on eastern North America, while for example the 'Road trip to LA' from the 'Life timeline example', the actual locations are to be found some place else.

A little improvement here could be to find the outer bounds of all POIs on the map, and to set the map extend to something a little larger on first load.