title: Use ipdb instead of pdb with py.test --pdb option
body: <p>I want to use <a href="https://pypi.python.org/pypi/ipdb" rel="noreferrer">ipdb</a> instead of <a href="https://docs.python.org/2/library/pdb.html" rel="noreferrer">pdb</a> with <a href="http://docs.pytest.org/en/latest/contents.html" rel="noreferrer">py.test --pdb</a> option. Is this possible? If so, how?</p>
  
  <p>Clearly, I can use <code>import ipdb; ipdb.set_trace()</code> in the code but that requires to run the test, watch it fail, open a file, find the point of failure in said file, write the above line, re-run the tests. Lots of hassle if I could have something that by passes all of that.</p>