Cleanup the repo a little bit after Rust Reference decision

There is still more two do, but this tries to at least reduce the confusion that this repo is actively being worked on at this point in time.

Author: JoelMarcey

README.md

@@ -1,25 +1,12 @@
 # The Rust Specification
 
-## Building
+## The Spec and the Rust Reference
 
-The specification uses [mdBook] to process the source into HTML. See [mdBook Installation] for more information on installing mdBook. To build the book, run:
+** The Rust specification is currently being developed as part of the [Rust Reference](https://github.com/rust-lang/reference).
 
-```sh
-mdbook build
-```
+The [`t-spec`](https://www.rust-lang.org/governance/teams/lang#team-spec) team, in consultation with interested parties from the Rust Project, made the decision on a [go-forward plan](https://hackmd.io/d-8LXh2NTASg7NF-zmZqNA?both#Review-go-forward-plan) that makes the Rust Reference the source of truth and the specification will be based on that content. 
 
-This will output the HTML into a directory called `book`.
-
-For authors, consider using the server functionality which supports automatic reload:
-
-```sh
-mdbook serve --open
-```
-
-This will open a browser with a websocket live-link to automatically reload whenever the source is updated.
-
-[mdBook]: https://rust-lang.github.io/mdBook/
-[mdBook Insallation]: https://rust-lang.github.io/mdBook/guide/installation.html
+It is currently unclear what happens to both this repository and the Rust reference once we are at a steady-state of having a usable specification. It is likely we will consolidate the two repositories into one that ends up being called the specification. Stay tuned for more information on that.
 
 ## License