Testing runtests on numpy.

[rainwoodman]

This is basically running numpy with pytest.

Here are some observations:

0. We need setuptools support. Newer numpy has switched to setuptools. This is PR Add support to setuptools based packages. #10

1. All tests needs to be patched to include __init__.py, due to the unique name workaround. see, e.g.
   "unique basename" error vs __init__.py in test sub-folders is a UX mayhem pytest-dev/pytest#529

2. Due to 1, some tests that does relative imports needs to be aware of the relative imports, requiring adding dots to the import lines.

3. A lot of yielded tests needs to be changed to parametrized tests.