Readme improvements

[larsbrinkhoff]

The readme file says:

Public Domain source code to the original DUNGEON game (Zork I).

The game known as "Zork I" was a microcomputer adaptation of the first part of the original Dungeon/Zork, see https://en.wikipedia.org/wiki/Zork_I
The PDP-10 version was called just "Zork" or "Dungeon" (actually both, as per 1977 source code). Supnik called his Fortran translation for the PDP-11 "Dungeon".

This version of dungeon has been modified from FORTRAN to C. The original was written in DEC FORTRAN, translated from MDL.

The MDL version was the original.