Convenience function for openvpn

Name is vpn. You pass it one argument, which is, essentially, the name of the
  VPN config file you want to use. However, it has one caveat, this function
  expects your config files to be named like: $1.client.ovpn. So $1 is what you
  would enter and it maps to the above.

An openvpn file for Google should be named:
  google.client.ovpn
And vpn called like:
  vpn google