AKtween ":append()" Implementation

example_append.lua

--Create a new AKtween
local tween = AKtween:newTween({time=5000, y=-600, ease='outQuad',
     onComplete={time=5000, y=600, ease='inQuad'}
})

--Append an existing AKtween
tween:append({time=10000, x=100, ease='outQuad'})

--Sample result:
--tween = {
--     arr = {
--          "y" = {-4.79, ... 0, ... 4.79},
--          "x" = {0.02, ... 2.43}
--     },
--     totFrames = 600
--}