Added license template, include in sdist

[TomAugspurger]

This adds the license file to the repository and sdist.

@matthewhanson @duckontheweb I've included the boilerplate from the Apache License. What would you like for the 'name of copyright owner' field?

[matthewhanson]

Thanks @TomAugspurger , @duckontheweb was the originator of the library so I think it should be him, I'll add it in.