Documentation/javadoc markup update.
Updated pom.xml: pinned this library to specific versions of dependencies instead of version ranges

This should make this library less annoying to use when you have
access to Maven Central Releases repository, but not to the
Snapshots repository. This occurs fairly often if you use a
local mirror of Maven Central.
Updated CHANGES.md for next release.
[maven-release-plugin] prepare release valueclasses-0.6