Add LICENSE

[Scheggetta]

Hi @kctess5 and @sertackaraman, me and many other users are using your great library, but in theory they should not be legally allowed to do so. In fact, if a public repository has no license, then it is automatically licensed as "all rights reserved".

Since I don't think this was your objective and 7 years have passed now, could you please consider adding a MIT or an Apache license (like RangeLibc)?

Thank you.