Add license info to Cargo.toml

[ralpha]

This will add the proper into to crate.io and others

[besok]

Thanks for the PR

[fbernier]

@besok would it be possible to cut a new 0.3.6 release with this change? cargo-about is failing without it, and since this crate is now used by the latest release of kube-client crate I expect more and more people will experience this problem.

Thanks!

[besok]

Ah. You are right. I forgot to bump up the version apparently. Thanks. Will do it tonight.