Propose a license for the code

Hi there. I'd like to possibly use this library on mozilla.org for some geo features we're adding. I do need to know under which license you're releasing this project however. I was going to create an issue but those don't seem to be enabled. Don't merge this, but please do add a license file or license text to the README if you do indeed want to release this code for use in other projects.

Thanks for the code!