Compiled functions only work with Python 3.8

[mzy2240]

Compiled functions are version dependent. Different python version cannot share the same compiled code. There are two ways to solve this:

1. compile the code during the installation, but this requires the environment has linked compiler (g++, clang, msvc) and linked blas library (mkl, for better performance);
2. compile multiple version during the release process, then import the corresponding file after checking the python version.

The second method brings extra procedure for the release process (though it could be automated), but it also gives users better performance without extra requirements.