title: drop column based on a string condition
body: <p>How can I delete a dataframe column based on a certain string in its name?</p>
  
  <p>Example:</p>
  
  <pre><code>           house1    house2    chair1  chair2
  index
    1         foo       lee       sam      han
    2         fowler    smith     had      sid
    3         cle       meg       mag      mog
  </code></pre>
  
  <p>I want to drop the columns that contain 'chair' in the string.
  How can this be done in an efficient way?
  Thanks.</p>