title: Calculate tf-idf weight for only given word list with sklearn
body: <p>I want to get tf-idf weights for given word list from the documents.
  for example, I have the words interested in like below.</p>
  
  <pre><code>document_list = ['''document 1 blabla''', '''document 2 blabla''']
  words = ['project', 'management', 'uml theory', 'wireframe']
  </code></pre>
  
  <p>Of course I can get terms and weights from documents using sklearn.
  but I want to get only the weight of above words from the document group using scikit-learn.
  Any idea will help me a lot.</p>