Support Geocode by PlaceId

[spaceraccoon]

geocode() does not support geocoding by placeId while reverse_geocode does.

[stephenmcd]

This isn't an issue with the client library since it simply implements whatever the web service provides: https://developers.google.com/maps/documentation/geocoding/intro

Seems like this has been supported recently.
Node JS implementation is already done.
googlemaps/google-maps-services-js#413