title: pandas.read_sql with sqlite is extremly slow
body: <p>I'm using pandas.read_sql with an sqlite Database and it is extremly slow. 
  I have a table with 800 rows and 49 columns (dataype just TEXT and REAL) and it takes over 3 Minutes to fetch the data from database to the dataframe. 
  The DB-File and the python script are running on the same machine and the same filesystem.</p>
  
  <p>Is there any way to speed up pandas.read_sql?</p>
  
  <p>This is the code fragment:</p>
  
  <pre><code>        self.logger.info('{} - START read_sql: {}'.format(table))
          result = pd.read_sql("select * from {}".format(table), self.dbconn,
                             index_col=indexcolname)
          self.logger.info('{} - END read_sql: {}'.format(table))
  </code></pre>