title: More than one estimator in GridSearchCV(sklearn)
body: <p>I was checking sklearn documentation webpage about <code>GridSearchCV</code>.
  One of attributes of <code>GridSearchCV</code> object is <code>best_estimator_</code>.
  So here is my question. How to pass more than one estimator to GSCV object?</p>
  
  <p>Using a dictionary like:
  <code>{'SVC()':{'C':10, 'gamma':0.01}, ' DecTreeClass()':{....}}</code>?</p>