If given a version_callback argument, Moose::Exporter will also produce
(or install) a VERSION method which will perform the core version check
but also call an arbitrary callback.

Using the version_callback feature, skip enabling strict and warnings if
Moose version 3 is requested. Any other module that uses Moose::Exporter
will continue to enable strict and warnings, as they are outside Moose
and don't follow its versioning.