title: pandas: read_csv how to force bool data to dtype bool instead of object
body: <p>I'm reading in a large flatfile which has timestamped data with multiple columns. Data has a boolean column which can be True/False or can have no entry(which evaluates to nan).</p>
  
  <p>When reading the csv the bool column gets typecast as object which prevents saving the data in hdfstore because of serialization error.</p>
  
  <p>example data: </p>
  
  <pre><code>A    B    C    D
  a    1    2    true
  b    5    7    false
  c    3    2    true
  d    9    4
  </code></pre>
  
  <p>I use the following command to read</p>
  
  <pre><code>import pandas as pd
  pd.read_csv('data.csv', parse_dates=True)
  </code></pre>
  
  <p>One solution is to specify the dtype while reading in the csv but I was hoping for a more succinct solution like convert_objects where i can specify parse_numeric or parse_dates.</p>