Remove reference to Google's DNS servers

Per discussion on #429 (after the merge). This project is about encouraging users to run services themselves and not rely on for-profit corporations such as Google.

Add SSL stapling cache for distributions with Apache 2.4+

Fixes #406

Closes #429

add additional comment about `tun-mtu` parameter in openvpn config template

- google dns setting for client
- verb level
- mtu
- TLS settings

Notes about security: https://blog.g3rt.nl/openvpn-security-tips.html
Check privacy: http://witch.valdikss.org.ru/

change auth to internal_hashed

Use common_timezone and fix idempotence

Add some info on DMARC

Thanks-to: 8e693b3db3

I ran a check on http://mail-tester.com and found out I was missing a header to be set for DMARC. SInce I missed it, maybe someone else missed it as well, so maybe it could go into the README.

Jessie

because why the fuck not?

Not awesome. We need a better alternative, ideally one with a better security stance.

Formatting the task names.

Use newer native "write HTTP" plugin to send metrics to Librato, if configured.