undefined symbol error for compiling with cython modules

A common error for installed packages (such as yt, caesar) which use cython to build parts of models:

` ImportError: /…**.cpython-36m-x86_64-linux-gnu.so: undefined symbol: __intel_sse2_strchr `

The solution is installing your package with specified compiler – icc:

` LDSHARED=”icc -shared” CC=icc python3 setup.py install –user `