title: Add days to date in pandas
body: <p>I have a data frame that contains 2 columns, one is Date and other is float number.
  I would like to add those 2 to get the following:</p>
  
  <pre><code>   Index           Date           Days           NewDate
       0           20-04-2016        5           25-04-2016
       1           16-03-2015       3.7          20-03-2015
  </code></pre>
  
  <p>As you can see if there is decimal it is converted as int as 3.1--> 4 (days).
  I have some weird questions so I appreciate any help.
  Thank you !</p>