title: Pandas how to convert a timestamp column (EST) to local TimeZone info available in other column
body: <p>From</p>
  
  <pre><code>colA (EST)                 colB (local tz) 
  2016-09-19 01:29:13        US/Central
  2016-09-19 02:16:04        Etc/GMT+2
  2016-09-19 01:57:54        Europe/London
  </code></pre>
  
  <p>To</p>
  
  <pre><code>colA (EST)                 colB (local tz)      colC (timestamp in local tz)    
  2016-09-19 01:29:13        US/Central           2016-09-19 02:29:13 
  2016-09-19 02:16:04        Etc/GMT+2            2016-09-19 08:16:04
  2016-09-19 01:57:54        Europe/London        2016-09-19 05:57:54  
  </code></pre>