Update Docs / examples - googleAPI and source = "dsk"

[YsoSirius]

All request that don't define source = "dsk" explicitly, fail with this warning:

geocode("houston texas")

geocode failed with status OVER_QUERY_LIMIT

Although there would still be remaining geocoding-calls available:

geocodeQueryCheck() 2482 geocoding queries remaining.

Could we make "dsk" the default instead of "google", as I think the google API now requires an API key. Otherwise all given examples in the docs fail too, which doesnt really look nice.