Change default network buffer size
Should increase tcp tunnel speed for openvpn < 2.3.9
https://community.openvpn.net/openvpn/ticket/461

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

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

  profiles

  * The role now generates .ovpn profiles with embedded CA, certificate,
    key, and HMAC firewall key information. These .ovpn profiles are
    compatible with OpenVPN for iOS and Android, and only a single file
    needs to be transferred to your mobile device.

  * Added explicit route information to the .ovpn profile

* Added 'cipher' and 'auth' lines to the generated client configs

OpenVPN role

correctly. The number of days that a certificate will be considered
valid is now a user-controlled variable and is set to five years by
default. (Fixes Issue #87)

 * Add an openvpn_server variable
 * Move ${openvpn_client}.{key,csr,crt} to
   ${openvpn_client}/client.{key,csr,crt}
 * Generate ${openvpn_client}/${openvpn_server}.ovpn config file
 * Copy over a self contained directory of file per client that can be
   imported by networkmanager in ubuntu or run directly with `sudo
   openvpn ${openvpn_server}.ovpn

  * OpenVPN setup is now fully automated. No configuration changes
    are necessary (though the defaults can easily be modified) and
    all manual command line steps have been eliminated.

  * Removed the dependency on easy-rsa in favor of pure OpenSSL and
    OpenVPN commands that are executed by Ansible

  * Improved the security of the OpenVPN configuration
    * Increased the default key size to 2048
    * RSA keys are only readable by root
    * The cipher and authentication digest are now configurable. If
      your client supports it, you can use AES-256-CBC and SHA256
      instead of BF-CBC (Blowfish) and SHA1 which are the defaults.
      Or you can be a really cool, paranoid, crypto hipster and
      use CAMELLIA-256-CBC and SHA512 with an RSA key size of 4096.
    * Enabled "HMAC firewall" functionality using the tls-auth option
      and automated the generation of the 'ta' key that it depends on
    * The OpenVPN daemon becomes an unprivileged user after it starts

  * Automated the retrieval of the files that clients will need in
    order to connect to OpenVPN

  * A pause prompt outputs basic configuration information after the
    role has finished running

  * Variables are referenced using the new Ansible variable format
    (e.g. {{ var }} instead of $var)

  * Added a flush_handlers command to the role that ensures OpenVPN
    will restart prior to dnsmasq (fixes issue #63)

  * Fixed two bugs that were preventing packet forwarding for IPv4
    from being enabled correctly

That way the default values will not be applied by mistake. The user
needs to uncomment the lines from `vars/users.yml` and set them.

Also renamed openvpn variables.

Refs #39