Relax limit on calling methods on unbound modules
Inspired by #636, relax the limitation on calling methods on unbound modules.
While at time users may be confused about when `setup` is run, hopefully
the new docstring we have on `setup` clarifies things. If users want
to write a method that doesn't depend on any attributes defined during
`setup` (e.g. submodules or variables), that should be fine.
