allow postgres unix sockets, simplify connection

Use by setting the 'host' setting to the directory of the postgres
socket (/tmp, /run/postgresql, /var/run/postgresql)
Merge pull request #27 from t-8ch/postgres_unix_sockets

allow postgres unix sockets, simplify connection
Merge pull request #28 from Pita/master

Master
Merge pull request #29 from Pita/develop

Develop