title: Disabling the previous date based on current date using angular material
body: <p>I found this snippet to disable the previous dates</p>
  
  <pre><code>&lt;md-datepicker 
             ng-model="myDate" 
             md-placeholder="Enter date"
             md-min-date="minDate" 
             md-max-date="maxDate"&gt;&lt;/md-datepicker&gt;
  </code></pre>
  
  <p>but instead of entering the minDate i want to assign the system date.
  pls do help</p>