Require rgeo-geojson with rgeo for easier conversions and wider support?

[camiloforero]

As the title says, I propose that if an user wants to install this gem with rgeos support, they will also be required to install the rgeos-geojson package.

If we do that, then we can replace the whole rgeo.rb wrapper by calls to this library, which has more built-in robustness and a variety of functions already implemented.

And this will make it much easier to add support to MultiPoint, MultiLineString and MultiPolygon classes in the future, as they are already supported by that library.

Would this kind of change and additional optional dependency be ok?

[dblock]

Sounds good to me.

[camiloforero]

Cool! I can start working on that then