Enhance testing: run all executables

Add a #! line at the beginning of each of the existing Python programs
and change these files to be executable. This sets the stage for having
the test script blindly run anything that is executable, adding support
for testing many programming languages.

02-code-golf/tf-02.py

@@ -1,3 +1,5 @@
+#!/usr/bin/env python
+
 import re, string, sys
 
 stops = set(open("../stop_words.txt").read().split(",") + list(string.ascii_lowercase))