Add a proper license

[Douglas Thor]

Love the project, but you probably want to add a proper license.

• The Open Source Initiate suggests not using Public Domain
• Why the Public Domain Isn’t a License

Slap the MIT License there and you're good to go.

[Forrest Smith]

The actual license embedded in the source is:

This software is dual-licensed to the public domain and under the following license: you are granted a perpetual, irrevocable license to copy, modify, publish, and distribute this file as you see fit.

I've updated the readme to make this clear.

[Douglas Thor]

Ah yes, I didn't see that. Perfect!

Sorry to bug you 😄