GoogleMapsProvider uses invalid url for reverse lookup

[arubacao]

The Google Maps Provider uses the same endpoint for geocode and reverse lookup.
https://github.com/geocoder-php/Geocoder/blob/master/src/Geocoder/Provider/GoogleMaps.php#L33

'https://maps.googleapis.com/maps/api/geocode/json?address=%s';

Unfortunately, this is the wrong endpoint (or rather param) for reverse lookup. Prove:

Reverse: https://maps.googleapis.com/maps/api/geocode/json?latlng=40.714224,-73.961452&key=YOUR_API_KEY

Geocode: https://maps.googleapis.com/maps/api/geocode/json?address=1600+Amphitheatre+Parkway,+Mountain+View,+CA&key=YOUR_API_KEY

Although it's currently not the correct endpoint, it somehow works since google is smart enough to figure that out.
However, if you want to use result_type or location_type as request parameters they will just be ignored. (Reference to #546)

I'm able to send a PR to fix this.

My approach:

1. Get inspired by how the other providers (e.g. BingMaps )handle different endpoints

2. Implement it for the GoogleMapsProvider

Please add your thoughts and comments & tell me if you approve this approach.
I'd appreciate a quick answer, so I can get started fast.

Cheers,
Chris

[Nyholm]

Closed by #551