Install reference to In-Reply-To: header.

  This updates #166.
  Simple code for message-id generation.

  This updates #166.
  Generate a convincing Message-ID.

  This updates #166
  Use the lua hostname() primitive.

  Now that I've remembered it exists ;)

  This updates #166
  Updated for the new utility ./util/dump-headers

  We now clean this binary when running :

    cd ./util && make clean

  We also ignore the generated binary from git.
  Remove "refresh_display()".

  `clear()` does the same job.

  (Poorly.)

  Closes #165.