Google Maps -> OpenStreet Maps

Switched to an open GMaps alternative.
Notes:
- rounded corners don't seem to work, so I set a nice 1 px #6B7770 border
- the default OSM tileset ("Mapnik") is too vivid for the colorset of the page so the more suitable MapQuest Open tileset is used
- it is my first ever Git commit, so please let me know if I screw something up. :)