title: Pandas read from csv parsing incorrectly large integers
body: <p>Hi i am having a problem.
  I am read from csv a file various columns and one of the columns is a 19 digit integer ID. The problem is if i just read it with no options the number is read as float. And in this case it seems to be mixing the numbers:
  For example the dataset has 100k of unique ID values but reading like that give me 10k unique values. I changed the read_csv options to read it as string and the problem remains while its being read as mathematical notation (eg: *e^18).</p>
  
  <pre><code>pd.set_option('display.float_format', lambda x: '%.0f' % x)
  df=pd.read_csv(file)
  </code></pre>