brew services stop postgresql
initdb /usr/local/var/postgres9.6 -E utf8
pg_upgrade -d /usr/local/var/postgres -D /usr/local/var/postgres9.6 -b /usr/local/Cellar/postgresql/9.5.5/bin -B /usr/local/Cellar/postgresql/9.6.1/bin -v
mv /usr/local/var/postgres /usr/local/var/postgres9.5
mv /usr/local/var/postgres9.6 /usr/local/var/postgres
brew services start postgresql