* build-aux/hydra/demo-os.scm (operating-system)[issue]: Point to
  shepherd instead of dmd.
* ROADMAP: Likewise.
* gnu/build/install.scm (directives): Adjust comment.

Suggested by Omar Radwan <toxemicsquire4@gmail.com>.

* ROADMAP: Rewrite.

* ROADMAP: Add link to the updated road map, and the a note on release
  history.

* ROADMAP: New file.
* Makefile.am (EXTRA_DIST): Add it.