Update XStream dependency.
Update XStream dependency.

There seems to be a problem with XStream version 1.2.2 that it does not
use enhanced mode and therefore requires default constructors for classes
to be serialized. The problem might be related to JDK 1.7 and/or MacOS.

mnuessler/cakupan-maven-plugin,mnuessler/cakupan-maven-plugin