[PR] Resolve postfix dependency, add www subdomains

While larger changes are being tested, we need to get these two into production.

* When PHP is installing it runs into some sort of dependency error with postfix and libmysql. To correct that, we install postfix using the CentOSPlus repositories.
* Any domains served by nginx should also respond to their `www` subdomain by redirecting via 301 to the main site.