Added visual success indicator (bootstrap glyphicon-ok)

* added ladda-success class for 1 second after lada.stop()
* added bootstrap glyphicon-ok

To benefit from the ladda-success class, here’s a simple CSS to use:

.ladda-success {
  .ladda-label {
	.glyphicon {
	  display:inline-block !important; //overrides default inline style
	}
  }
}