title: Spark custom vocabulary for CountVectorizer and IDF
body: <p><code>CountVectorizer</code> will produce its own list of indices based on entries, e.g.</p>
  
  <pre><code>"I Spark"
  "Spark need boy"
  </code></pre>
  
  <p>will produce</p>
  
  <pre><code>(4, idicies=(1,2), values=(1,1))
  (4, indicies=(2,3,4), values=(1,1,1))
  </code></pre>
  
  <p>but I'd like to pass my own vocabulary with, say, ("I":10, "Spark":123,"need":3, "boy":99) so:</p>
  
  <pre><code>(4, idicies=(10, 123), values=(1,1))
  (4, indicies=(123,3,99), values=(1,1,1))
  </code></pre>
  
  <p>Is this possible? Same for IDF?</p>