/usr/local/var/postgresがあれば削除する
$brew install postgresql
$brew uninstall postgresql
$brew uninstall --force postgresql
$brew install postgresql
$initdb /usr/local/var/postgres -E utf8
$postgres -D /usr/local/var/postgres
$export PGDATA=/usr/local/var/postgres
$pg_ctl start
$pg_ctl stop
$pg_ctl start -l /usr/local/var/postgres/server.log
$psql -l
$createuser -P user
参考URL
http://open-groove.net/postgresql/mac-brew-postgresql/
http://qiita.com/_daisuke/items/13996621cf51f835494b
http://stackoverflow.com/questions/27700596/homebrew-postgres-broken