title: Convert dd/mm/yyyy H to date format
body: <p>I have the following column in R</p>
  <pre><code>dteday = c(&quot;01/01/2011 0&quot;, &quot;01/01/2011 1&quot; , &quot;01/01/2011 2&quot;, &quot;01/01/2011 19&quot;)
  df = data.frame(dteday)
  </code></pre>
  <pre><code>        dteday
  1  01/01/2011 0
  2  01/01/2011 1
  3  01/01/2011 2
  4  01/01/2011 19
  </code></pre>
  <p>I want the column to be converted into a proper %d/%m/%Y H:M format
  The string on the left is in %d/%m/%Y format while the integer on the right is the hour. The integer on the right represents the hour / time. This is my desired output</p>
  <pre><code>        dteday
  1  01/01/2011 00:00
  2  01/01/2011 01:00
  3  01/01/2011 02:00
  4  01/01/2011 19:00
  </code></pre>