dbus: expose NewConnection method (#153)
dbus: expose NewConnection method (#153)

By providing a callback to NewConnection, users can now initialise a session over a transport of their choosing
jonboulle/go-systemd,coreos/go-systemd,endocode/go-systemd,glerchundi/go-systemd,jonboulle/go-systemd,glerchundi/go-systemd,endocode/go-systemd,coreos/go-systemd