Implemented CCEasePolynomial Action.

- Developed a replacement for exponential mathematical routine with a nth order polynomial which resembles an exponential curve for values of 0 <= t <= 1 and an order of 6.
- Advantage of using polynomial curves is that they do not asymptote.
- Developers can control the acceleration at which it eases in or out by adjusting the polynomial value, polynomial must be greater than 1.
- Allowed for odd and even values of polynomial orders as odd values will exhibit an inflection in the curve.
Updates AUTHORS and CHANGELOG