title: Converting time zone pandas dataframe
body: <p>I have data:</p>
  <pre><code>                             Symbol      bid      ask
  Timestamp                                            
  2014-01-01 21:55:34.378000  EUR/USD  1.37622  1.37693
  2014-01-01 21:55:40.410000  EUR/USD  1.37624  1.37698
  2014-01-01 21:55:47.210000  EUR/USD  1.37619  1.37696
  2014-01-01 21:55:57.963000  EUR/USD  1.37616  1.37696
  2014-01-01 21:56:03.117000  EUR/USD  1.37616  1.37694
  </code></pre>
  <p>The timestamp is in GMT. Is there a way to convert that to Eastern?</p>
  <p>Note when I do:</p>
  <pre><code>data.index
  </code></pre>
  <p>I get output:</p>
  <pre><code>&lt;class 'pandas.tseries.index.DatetimeIndex'&gt;
  [2014-01-01 21:55:34.378000, ..., 2014-01-01 21:56:03.117000]
  Length: 5, Freq: None, Timezone: None
  </code></pre>