MAINT add that pytest >= 3 is required in README.rst
MAINT add that pytest >= 3 is required in README.rst

aabadie/joblib,tomMoral/joblib,aabadie/joblib,karandesai-96/joblib,joblib/joblib,joblib/joblib,lesteve/joblib,karandesai-96/joblib,tomMoral/joblib,lesteve/joblib