Update license information in the read me

README.md

@@ -166,14 +166,9 @@ loser who jumped on the train, don't give me any money.
 #### License
 
 <sup>
-Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
-2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.
-</sup>
-
-<br>
+Licensed <a href="LICENSE-MIT">MIT license</a> at your option.
 
-<sub>
-Unless you explicitly state otherwise, any contribution intentionally submitted
-for inclusion in this crate by you, as defined in the Apache-2.0 license, shall
-be dual licensed as above, without any additional terms or conditions.
-</sub>
+Any contribution must be accompanied with a signature of the
+[Developer Certificate of Origin](https://developercertificate.org/),
+by using the `--signoff` flag on `git commit`.
+</sup>