Bear in mind, that since it's on github, even though it's a 'quick and dirty job', people WILL just download it, run it and expect it to work, and if it works, not care about auditing the code.

Those people deserve what they get, maybe, but still. Getting into a habit of never releasing anything that doesn't at least have basic security is a good idea.

When you come around to hashing the passwords consider https://github.com/rchouinard/phpass