README: Drop '32-bit only', mention Pyhton 3 and raise required Python to 2.5+
README: Drop '32-bit only', mention Pyhton 3 and raise required Python to 2.5+

theblacklion/pyglet,oktayacikalin/pyglet,theblacklion/pyglet,theblacklion/pyglet,oktayacikalin/pyglet,theblacklion/pyglet,oktayacikalin/pyglet,oktayacikalin/pyglet,theblacklion/pyglet,oktayacikalin/pyglet