Buffer abstractions.

This includes a common, plataform agnostic abstractions defined
with clojure protocols for treat with different bytebuffers
implementations.

Also inclues a polymorphic methods for allocate new bytebuffers
with support for nio bytebuffers, netty41 bytebuffers and
es6 typed arrays (from javascript environments).

The spec abstraction.

It includes the basic abstraction protocols for define
own type specs and some useful types that allows build
asociative or indexed spec compositions.

For more examples see the `spec` function docstring.

Spec types for arbitrary length byte arrays/strings with a length reference.