Move tests out of the installed package set

this seems to be better practice. from what i can tell this is a
clean move with no breakage.. and built package files no longer seem
to include test modules

Make 'tests' a proper subpackage again; add some tests

Trying to make more of an effort here...

Add `User.get_email_address()` and `User.email_address`.

For now, these will do. Probably need to revisit that at some point.