Bump version to 3.0.0-dev

Yes, Geocoder 3 has begun!
Move IpGeoBase provider to geocoder-extra (#342)
Move Baidu provider to geocoder-extra (#341)
Move DataScienceToolkit provider to geocoder-extra (#340)
Remove `OpenStreetMapsProvider` class (close #335)
Move GeoCoder.ca provider to geocoder-extra (close #337)
Move GeoCoder.us provider to geocoder-extra (close #338)
Move OIORest provider to geocoder-extra (#336)
Move IGN OpenLS provider to geocoder-extra (close #339)
Added headers handling to geocoder
Added headers handling to geocoder