Add .md extension to README

So that it looks pretty on GitHub.
Indent code snippets
Update heading style

This is purely my personal preference.
Update Capfile

To point to the new server and to deploy from this branch.
Update Capfile

Add tasks to update the Apache config and restart the web server.
Update ServerName in Apache config

I'll change this back when we're ready to make the switch to the new server.
Use PassengerUser instead of PassengerDefaultUser

We want to start the Passenger process as freerange so that it can
access the environment variables set within that user's shell.

I'm not sure why we were previously setting `PassengerDefaultUser` but
it doesn't appear to do what we need.
Remove SMTP_PASSWORD from Apache config

We can set this as an environment variable in the freerange user's
profile (by using `cap env:edit`) rather than having to store it in the
Apache config.
Add `Require all granted` to avoid 403 errors

As per the Apache upgrading instructions[1].

[1]: http://httpd.apache.org/docs/2.4/upgrading.html#access
Update README with deployment instructions