title: Does pip handle extras_requires from setuptools/distribute based sources?
body: <p>I have package "A" with a setup.py and an <a href="https://pythonhosted.org/setuptools/setuptools.html#declaring-extras-optional-features-with-their-own-dependencies" rel="noreferrer">extras_requires</a> line like:</p>
  
  <pre><code>extras_require = {
      'ssh':  ['paramiko'],
  },
  </code></pre>
  
  <p>And a package "B" that depends on util:</p>
  
  <pre><code>install_requires = ['A[ssh]']
  </code></pre>
  
  <p>If I run <code>python setup.py install</code> on package B, which uses <code>setuptools.command.easy_install</code> under the hood, the <code>extras_requires</code> is correctly resolved, and paramiko is installed.</p>
  
  <p>However, if I run <code>pip /path/to/B</code> or <code>pip hxxp://.../b-version.tar.gz</code>, package A is installed, but paramiko is not.</p>
  
  <p>Because pip "installs from source", I'm not quite sure why this isn't working. It should be invoking the setup.py of B, then resolving &amp; installing dependencies of both B and A.</p>
  
  <p>Is this possible with pip?</p>