run postgresql in foreground - refs #50

I still haven't figured out logs. 

All I could think of is redirecting process output, which requires starting executor with shell=True, BUT, we can't properly close executor then - https://github.com/ClearcodeHQ/mirakuru/issues/27
Not to mention, that I haven't been able to get anything in redirected output anyway.

See `bindir/postgres --help`