Add numpy and cython to setup requirements

[assafmus]

I added the numpy and cython to setup.py requirements.
This enables pip installing this repo without having to manually install numpy and cython beforehand.

I'm still getting this error:

I'm not sure if this change is 100% ready but it works for me and the test pass.

[lig]

@gatagat what do you think about this one?

[gatagat]

I don't think this is solving the issue. The install_requires setting is for runtime dependencies, not setup time dependencies. So adding cython/numpy to install_requires will not ensure that it is installed when setup.py runs and these packages are needed.

There are three possibilities:

1. Avoid requiring those packages at setup time by pre-generating and distributing the cythonized pyx file.
2. Avoid requiring the setup itself as per PEP517/518 + e.g. flit.
3. Publish wheels for major systems making it even simpler for users (no compiler required).