Dependency updates

- use mesos 0.20.1 release
- use undertow bugfix 1.0.16.Final
add changelog
update readme a bit
Update to mesos 0.20.1 protocol.
add some missing fields to the pom
[maven-release-plugin] prepare release jesos-1.0
[maven-release-plugin] prepare for next development iteration
Replace deprecated methods from Guava Objects

This change requires guava 18.0 or newer.