title: Default pip installation of Dask gives "ImportError: No module named toolz"
body: <p>I installed <a href="https://github.com/dask/dask" rel="noreferrer">Dask</a> using pip like this:</p>
  
  <pre><code>pip install dask
  </code></pre>
  
  <p>and when I try to do <code>import dask.dataframe as dd</code> I get the following error message:</p>
  
  <pre><code>&gt;&gt;&gt; import dask.dataframe as dd
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File "/path/to/venv/lib/python2.7/site-packages/dask/__init__.py", line 5, in &lt;module&gt;
      from .async import get_sync as get
    File "/path/to/venv/lib/python2.7/site-packages/dask/async.py", line 120, in &lt;module&gt;
      from toolz import identity
  ImportError: No module named toolz
  No module named toolz
  </code></pre>
  
  <p>I noticed that <a href="http://dask.pydata.org/en/latest/install.html#pip" rel="noreferrer">the documentation</a> states</p>
  
  <blockquote>
    <p><code>pip install dask</code>: Install only dask, which depends only on the standard library. This is appropriate if you only want the task schedulers.</p>
  </blockquote>
  
  <p>so I'm confused as to why this didn't work.</p>