default zoom level is defined in the json describing city places.

this allow city to start with a zoom adapted to its size.
For exemple, 14 is nice for Toulouse, but London won't in the screen with a zoom of 14 (13 is nice for London)
clean dead code from a previous spike.

(i should be honest : i should never have commit it. I have to better read my diff when commiting).
Merge pull request #2 from avernois/add_zoom_level_per_city

Add zoom level per city