Tween Enhancments

@ndonald2 I added a few things to expanding our tweening capabilities.  Let me know what you think.
I'm not 100% sure which post I got them from.  I looked around for a lot of different easing functions.  The last few I remember were from:
https://github.com/warrenm/AHEasing/blob/master/AHEasing/easing.c
https://github.com/domhofmann/PRTween/blob/master/lib/PRTweenTimingFunctions.m
and this blog post
http://iphonedevelopment.blogspot.com/2010/12/more-animation-curves-than-you-can.html

There are probably a few more functions that we can add as well if we want to expand it.