Setup Google Mail rather than basic SMTP

The default sendmail setup can easily get blocked by spam-prevention
services. Configure the host to act as a mail client rather than a
mail transfer agent, to prevent problems.
Point Rails config to sendmail for email

With our complex DNS configs, connecting directly using SMTP can get
a host blocked by spam filters. Using sendmail as a mail client to a
proper mail agent is safer.
Merge branch 'smtp' into player