S2 geometry library porting

[pavankumarjs]

@nabeelamjad The S2 geometry cells which are natively implemented in ruby will be very helpful in my project. The Lat-Long to cell id conversion code is ported from the S2 Geometry library. But the cell id to lat-long conversion is not available in this gem. Can you help me to port the rest of the library? And guide me with the required resources for porting the library?

[nabeelamjad]

@pavankumarjs have a look at https://github.com/qedus/sphere/blob/master/sphere.py, that's essentially where I've ported from.