Add a License

[adelmott]

Without a license specified, no one can use this code. https://github.com/readme/guides/open-source-licensing

[MortenTabaka]

Hey @andrewdcampbell,

If you created this project with the intention of it being re-used, could you please add a license? I noticed that your other repositories have the GPL-3.0 license.

Your project is like a dream come true!

Best regards,
Marcin