upvote pulse animation

pulse.cs

			var pulseAnimation = CABasicAnimation.FromKeyPath ("transform.scale");
			pulseAnimation.Duration = 0.15;
			pulseAnimation.To = NSNumber.FromFloat(1.5f);
			pulseAnimation.TimingFunction = CAMediaTimingFunction.FromName(CAMediaTimingFunction.EaseInEaseOut);
			pulseAnimation.AutoReverses = true;
			pulseAnimation.RepeatCount = 2;
			_upvoteView.Layer.AddAnimation (pulseAnimation, "scalepulse");