Guide for Bindings, auto link bindings

- Add support for auto-linking bindings like:
  - `data-#{binding}` to API docs entry (if present)
  - `data-#{binding}-#{arg}` to `data-#{binding}` entry (if present)
- Write bindings guide -- mostly copied from API docs (removed [in this PR](https://github.com/batmanjs/batman/pull/1013))

I'd really appreciate a review of [the guide](https://raw.githubusercontent.com/batmanjs/batmanjs.github.io/d220603c1dfd6d48cd8ad04f7d55729b95588af0/docs/bindings.md), especially if anyone has any "Shouldn't it say something about..." or "I wish someone had told me... " type things!

@danott @zhubert @chantastic @TheBerg  @danielmurphy @mranallo @sdomino @jouh, if any of you has a few minutes, I'd appreciate it!