The /etc/postfix directory needs to be owned by the postfix user

Fixes #2.

There's currently a bug in Ubuntu 12.04 TLS where the /etc/postfix
directory is owned by root and postfix has an issue creating the
sasl_passwd.db when postfix_smtp_sasl_auth_enable option is enabled.
Merge pull request #3 from balanced-ops/develop

The /etc/postfix directory needs to be owned by the postfix user