Use the platform-independent way of calling a script from the shell: "python prog.py", not "prog.py"

Found by Micheal Wells on docs@.

Patch by Filip Gruszczyński.

Fix order of required StreamReader/StreamWriter base classes.  Spotted by Edward Welbourne on docs@.

Found by Helge Stenström on docs@.

Fix markup to not add parens to the "hashlib.md5" constructor when the object is meant, not the call.