title: split rows in pandas dataframe
body: <p>I stuck with the problem how to divide a pandas dataframe by row,</p>
  <p>I have a similar dataframe with a column where values are separated by \r\n and they are in one cell,</p>
  <pre class="lang-py prettyprint-override"><code>    Color                              Shape  Price
  0  Green  Rectangle\r\nTriangle\r\nOctangle     10
  1   Blue              Rectangle\r\nTriangle     15 
  </code></pre>
  <p>I need to divide this cell into several cells with the same values as other columns, e.g.</p>
  <pre class="lang-py prettyprint-override"><code>   Color      Shape  Price
  0  Green  Rectangle     10
  1  Green   Triangle     10
  2  Green   Octangle     10
  3   Blue  Rectangle     15
  4   Blue    Tringle     15
  </code></pre>
  <p>How do I do it well?</p>