make gzip binary status explicit
make gzip binary status explicit

Python gzip docs say that modes missing 'b' get it added silently.
Better to make the binary mode more visible.

JDReutt/BayesDB,poppingtonic/BayesDB,JDReutt/BayesDB,JDReutt/BayesDB,JDReutt/BayesDB,JDReutt/BayesDB,poppingtonic/BayesDB,poppingtonic/BayesDB,poppingtonic/BayesDB,poppingtonic/BayesDB