title: IPython Notebook ipywidgets does not show
body: <p>I created a table with an interactive slider that allows me to toggle between different periods on my table. It was working for the past few days, until today, when I re-ran the notebook, the slide bar doesn't show anymore. No error messages appear. The code seem to run just fine, as the table appears, but the slide bar just doesn't appear. I didn't change my code either, as I was working on a separate part of my notebook. </p>
  
  <p>I tried many approaches, including searching in this space but was still unable to come up with a solution. I was wondering if anyone faced a similar issue, and have any solution to this.</p>
  
  <p>Below is my code snippet. Anything before was solely to get my data into the desired form for tabulation. </p>
  
  <pre><code>from IPython.display import display
  from ipywidgets import widgets, interactive
  v = interactive(by_q, quarter=(['q1y2015', 'q2y2015', 'q3y2015', 'q4y2015']), days=(1, 180))
  display(v)
  </code></pre>