Functors (and Monads) in Rust

This crate provides functors and monads in Rust. The API is designed to allow additional bounds on inner types, thus allowing implementation of a common Functor trait for all collections in std::collections, including those which have an Eq + Hash or an Ord bound on their relevant methods.

Also included in this crate are Functor and Monad implementations for boxed iterators, futures, and functions.