reporter_that_creates_an_approval_script doesn't work on Windows

[JayBazuzi]

• It writes a .sh file, should be .cmd
• It writes Unix-style newlines (\n), should be Windows-style (\r\n)
• It writes a Bash shebang header (#!/bin/bash), should not

Also, neither Windows nor Unix-like scripts have any error handling; maybe that is OK.

Also, tests!

Suggestion: separate out a data structure that describes what needs to be done from a "formatter" that writes it as a script.