Take element height into consideration in colorize function

[damirkotoric]

The colorise function now takes the element height into consideration
when animating, which makes the animation look as intended when the
switch is customised.

[damirkotoric]

Before:

After:

[abpetkov]

I can't merge this as it is right now. What I agree on, is that the shadow behaviour is not 100% equivalent to the native iOS7 switch - the shadow animation should end before the handle animation. But you're just changing the size, which as we can see in your preview, leaves a slight transparent layer over the switch color during animation. And this doesn't make it any better. Honestly, I like it better as it is now.

So if you're willing to do try to mimic iOS7 behaviour and make it exactly the same, I'll be glad to review that.

P.S. This is the default iOS7 behaviour: