velocity.ui: Prevent display none at out-animations with new option

Hey,

in one of my projects i used velocity(.ui) to animate some texts and images IN/OUT based on the scroll position.
This works great, if i set the element to <code>opacity:0;</code> and animate it IN with <code>$elem.velocity("transition.slideUpIn")</code>.
But when i animate the element out the other content jump up. Not very nice.

To fix that problem i added the option <code>opacity: true/false;</code>. On true the out-animation will not reset the css of the element to <code>opacity:1; display:none;</code>

Example of the problem and the new option:
http://codepen.io/anon/pen/JyroK