title: Difference between parse_date=[0] and parse_date=True in pandas.read_csv
body: <p>This code:</p>
  
  <pre><code>import pandas as pd
  from StringIO import StringIO
  
  data = "date,c1\n2012-07-31 02:00,1.1\n2012-07-31 02:15,2.2\n2012-07-31 02:30,3.3\n"
  
  df1 = pd.read_csv(StringIO(data),parse_dates=True).set_index(('date'))
  df2 = pd.read_csv(StringIO(data),parse_dates=[0] ).set_index(('date'))
  
  print "df1:\n{index}".format(index=df1.index)
  print "df2:\n{index}".format(index=df2.index)
  </code></pre>
  
  <p>returns:</p>
  
  <pre><code>df1:
  array([2012-07-31 02:00, 2012-07-31 02:15, 2012-07-31 02:30], dtype=object)
  df2:
  &lt;class 'pandas.tseries.index.DatetimeIndex'&gt;
  [2012-07-31 02:00:00, ..., 2012-07-31 02:30:00]
  Length: 3, Freq: None, Timezone: None
  </code></pre>
  
  <p>Is this difference between df1 and df2 a bug,feature, or have I misunderstood something? </p>