Yap: Yet another (rust) parsing library

A lightweight, dependency free, parser combinator inspired set of utility methods to help with parsing input.

The goal of Yap is to provide a lightweight, easy to understand interface that exposes common, parser combinator style methods to make it easy to parse things (currently strings and slices, but it can be user-extended to other types), but also ensure that errors can be easily created and propagated, and things like location information are readily accessible.