title: Carbon difference between two dates to get a decimal for hourly rate calculations
body: <p>I am using Carbon to calculate the time between two dates. I'd like to be able to take difference between two dates and determine the time in decimal format to be able to calculate hourly rate. From my testing, the ->diffInHours() call gives me the hours between two dates in whole numbers. </p>
  
  <p>For example</p>
  
  <pre><code>$actual_start_at = Carbon::parse('2017-05-01 13:00:00');
  $actual_end_at = Carbon::parse('2017-05-01 15:15:00');
  return $actual_end_at-&gt;diffInHours($actual_start_at, true);
  </code></pre>
  
  <p>Returns</p>
  
  <pre><code>2
  </code></pre>
  
  <p>I would like something that returns to get the <code>2 hours 15 minutes</code></p>
  
  <pre><code>2.25
  </code></pre>