windows build `build_cpu_nms.sh` need to change setting.

[Animadversio]

This is a fantastic package!

I noted that trying to build_cpu_nms on Windows system will throw an compilation error about '/Wno-cpp'

cl : Command line error D8021 : invalid numeric argument '/Wno-cpp'

This is related to this issue mentioned in cocodataset https://github.com/cocodataset/cocoapi/issues/51

The quick fix to it is to change L47 in FaceBoxes\utils\build.py from extra_compile_args=["-Wno-cpp", "-Wno-unused-function"],# to extra_compile_args={'gcc': ['/Qstd=c99']},#["-Wno-cpp", "-Wno-unused-function"],