Random Access Zippers

This is untested WIP open to issues and PRs.

A data structure to represent sequences with fast random access.

Data.Raz.Sequence is intended to provide the same interface as Data.Sequence from containers.

Data.Raz.Core is the actual zipper module. It is a simple translation of the OCaml implementation the original paper appeared with.

• The Random Access Zipper: Simple, Purely-Functional Sequences