prefer Moose if Moo is loaded

Porting a module from Any::Moose to Moo will cause some
incompatibilities.  Subclasses that are still using Any::Moose will
attempt to use Mouse by default, which will fail to inherit from the Moo
class properly.  Moo has special handling to allow Moose to inherit from
it sanely, so prefer to use Moose if possible when Moo is loaded.
Merge pull request #1 from haarg/moo-compat

prefer Moose if Moo is loaded