Binary AST (Stage 1)

Champions: @syg, @vdjeric, @Yoric, @kannan-vijayan
Spec Repo: https://github.com/syg/ecmascript-binary-ast/
First presented at the July 2017 meeting: https://github.com/tc39/agendas/blob/master/2017/07.md

## Why is this relevant

Babel operates on an AST, and would be part of the toolchain that should be able to take advantage of this format. This would help consolidate tooling to use the same AST. Would be a breaking change, unless our AST is adopted (unlikely, and probably not desired).

Start by reading the linked ECMAScript binary AST spec repository and the July 2017 TC39 agenda entry. No Babel files, tests, concrete implementation steps, or acceptance criteria are named, so the scope and definition of done require maintainer clarification before work can begin.

Written by the indexing model from the issue text.