fix Makefile and README.md for 2018/burton2

Rename `README.txt` to `READ_ME.txt`.

Help shell scripts to find the shell and make them executable.

2018/burton2/unob.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
 # unob is a proof-of-concept script.
 # Prior to tac, scripting the layout of C code was intractable.