Revisit pytest config

- add testpaths setting
- tox: remove testpaths from posargs default
- s/py.test/pytest/

pytest.ini

@@ -10,3 +10,5 @@ norecursedirs = .* docs completion refactor absolute_import namespace_package
 # fine as long as we are using `clean_jedi_cache` as a session scoped
 # fixture.
 usefixtures = clean_jedi_cache
+
+testpaths = jedi test