Add LICENSE section to README

Author: Korbik

README.md

@@ -34,3 +34,14 @@ mvn clean install
 # skip tests
 mvn clean install -DskipTests
 ```
+
+## License
+
+Licensed under Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally
+submitted for inclusion in the work by you, as defined in the Apache-2.0
+license, shall be licensed as above, without any additional terms or
+conditions.