Develop v2 ease exponential

Modified the exponential ease actions so as to remove the asymptotes present in exponential curves by replacing with a nth order polynomial curve. Refer to commit comments for detailed explanation and the problems asymptotes cause in animation.

The attached image shows the following:
Purple curve = Exponential Curve for EaseOut, asymptotes at y = 1
Red curve = 6th order polynomial for EaseOut, y =1 when x = 1
Green curve = Exponential Curve for EaseIn, asymptotes at y = 0
Dark Blue curve = 6th order polynomial for EaseIn, y =0 when x = 0
Brown and light blue curve represent an EaseInOut 6th order polynomial were y = 0 when x = 0 and y = 1 when x = 1.

![CCEasePolynomial](https://f.cloud.github.com/assets/1904325/227130/e153de9e-8651-11e2-8802-aa1c0d9e60b5.png)