Implement custom type and custom overflow

[maximveksler]

It could be super cool if we’d implemented an overflow / override the << operator for bit so that when we reach 0b00001 it would overflow to 0b10000 automatically. This would simplify and beautify the code.

See here https://github.com/maximveksler/GeohashKit/blob/master/GeohashKit/Geohash.swift#L86

Assuming swift supports something like this now, or in the future. “)