Declare plexus-util dependency to a newer version

[npepinpe]

It seems Maven 3 has a weird feature to be compatible with Maven 2, where any extension which doesn't declare an explicit plexus-util dependency will get it injected with the 1.1 version.

Since this is dynamic, the dependency plugin doesn't "know" that it's present and thus when you use the go-offline goal, this dependency isn't resolved. It might be simpler then to just add an explicit plexus-util dependency here so that it plays nice with the rest of the ecosystem.

Alternatives is that anyone including this plugin and who wants to go-offline, or wants to enforce dependency convergence, needs to set the plexus utils dependency manually when declaring the plugin.

Source: https://issues.apache.org/jira/browse/MNG-6965