title: Merge rows within a group together
body: <p>I have a pandas DataFrame where some pairs of rows have the same ID but different name.  What I want is to reduce the row pair to one row, and display both of their names.</p>
  
  <p>INPUT:</p>
  
  <pre><code>ID   NAME     AGE
  149  Bob      32
  150  Tom      53
  150  Roberts  53
  151  Pamela   28
  152  Andrew   23
  </code></pre>
  
  <p>OUTPUT:</p>
  
  <pre><code>ID   NAME        AGE
  149  Bob         32
  150  Tom Roberts 53
  151  Pamela      58
  152  Andrew      23
  </code></pre>
  
  <p>Otherwise, I can also do ['Tom', 'Roberts'], or any other method that still captures the data.</p>