An N-Body simulation program using all-pair algorithm

Todos:

10, Rewrite the datasaving codes.

20, Rewrite the rendering code. (Maybe in C instead of Python.)

21, Change the rendering method. (Maybe something more mathematical, but not that mathematical.)

30, Support computing on multiple devices. (Since I haven't multiple GPUs in one PC, this might take some times.(sad))

40, Support distributed computing. (Emmm.)