fix(postgres): postgres version bumped

Postgres version bumped to fix silent lamassu-install error:

> Obsolete major version 9.3
>
> The PostgreSQL version 9.3 is obsolete, but the server or client
> packages are still installed. Please install the latest packages
> (postgresql-9.4 and postgresql-client-9.4) and upgrade the existing
> clusters with pg_upgradecluster (see manpage).
>
> Please be aware that the installation of postgresql-9.4 will
> automatically create a default cluster 9.4/main. If you want to upgrade
> the 9.3/main cluster, you need to remove the already existing 9.4
> cluster (pg_dropcluster --stop 9.4 main, see manpage for details).
>
> The old server and client packages are no longer supported. After the
> existing clusters are upgraded, the postgresql-9.3 and