Python Setup.md

1. Error

1. XGBoost Install Error

https://stackoverflow.com/a/43101972/2776008

brew install gcc --without-multilib
git clone --recursive https://github.com/dmlc/xgboost
cd xgboost; cp make/config.mk ./config.mk
vi config.mk

Uncomment the lines near the top of the file:

export CC = gcc
export CXX = g++

Change them to the following:

export CC = gcc-7
export CXX = g++-7

make clean_all && make -j4
cd python-package; python setup.py install