title: ImportError: cannot import name 'DeprecationDict'
body: <p>I'm trying to import dask_searchcv and error is thrown while import other module <code>DeprecationDict</code>. </p>
  
  <p>I have installed dask_searchcv Version: 0.2.0, and scikit-learn
  Version: 0.21.3</p>
  
  <p>I tried importing the dark_searchcv as shown below:</p>
  
  <pre class="lang-py prettyprint-override"><code>import dask_searchcv as dcv
  </code></pre>
  
  <p>I'm getting the following error message:</p>
  
  <pre class="lang-py prettyprint-override"><code>ImportError                               Traceback (most recent call last)
  &lt;ipython-input-19-b8082b897401&gt; in &lt;module&gt;
        1 # Instantiate the grid search model
  ----&gt; 2 import dask_searchcv as dcv
        3 # grid_search = dcv.GridSearchCV(estimator = rf, param_grid = param_grid, cv = 3)
        4 # grid_search.fit(data, target)
        5 # grid_search.best_params_
  
  ~/.virtualenvs/dask-test/lib/python3.6/site-packages/dask_searchcv/__init__.py in &lt;module&gt;
        1 from __future__ import absolute_import
        2 
  ----&gt; 3 from .model_selection import GridSearchCV, RandomizedSearchCV
        4 
        5 from ._version import get_versions
  
  ~/.virtualenvs/dask-test/lib/python3.6/site-packages/dask_searchcv/model_selection.py in &lt;module&gt;
       52 
       53 if _SK_VERSION &gt;= '0.19.1':
  ---&gt; 54     from sklearn.utils.deprecation import DeprecationDict
       55     _RETURN_TRAIN_SCORE_DEFAULT = 'warn'
       56 
  
  ImportError: cannot import name 'DeprecationDict'
  </code></pre>
  
  <p>I have tried re-installing sklearn using <code>pip3 install -U scikit-learn</code> but issue still remains unresolved.</p>
  
  <p><strong>Note: I'm running above code using jupyter notebook</strong></p>