title: tz_convert in pandas does not work for any city in India
body: <p>the below command seems to work for a other locations in Asia except for any location in India. Is there a bug here or am I missing something?
  this works:</p>
  
  <pre><code>pd.to_datetime(pd.datetime.now()).tz_localize('US/Pacific').tz_convert('Asia/Hong_Kong')
  pd.to_datetime(pd.datetime.now()).tz_localize('US/Pacific').tz_convert('Asia/Karachi'
  pd.to_datetime(pd.datetime.now()).tz_localize('US/Pacific').tz_convert('Asia/Dubai')
  </code></pre>
  
  <p>this does not work with exactly the same format (like any location in India):</p>
  
  <pre><code>pd.to_datetime(pd.datetime.now()).tz_localize('US/Pacific').tz_convert('Asia/New_Delhi')
  </code></pre>
  
  <p>throwing the below error</p>
  
  <pre><code>File "C:\Miniconda\lib\site-packages\pytz\__init__.py", line 180, in timezone
  raise UnknownTimeZoneError(zone) UnknownTimeZoneError: 'Asia/New_Delhi'
  </code></pre>