title: python setup.py sdist only including .py source from top level module
body: <p>I have a setup.py:</p>
  
  <pre><code>from setuptools import setup
  
  setup(
        ...
        packages=['mypackage'],
        test_suite='mypackage.tests',
        ...
      )
  </code></pre>
  
  <p><code>python setup.py sdist</code> creates a file that includes only the source modules from top-level mypackage and not mypackage.tests nor any other submodules. </p>
  
  <p>What am I doing wrong?</p>
  
  <p>Using python 2.7</p>