Update Readme.markdown

ifconfig inside openvpn::client_specific_config should not contain "<IP address> <mask>" but "<IP address 1> <IP address 2>", where "Each pair of ifconfig-push addresses represent the virtual client and server IP endpoints." (from https://openvpn.net/index.php/open-source/documentation/howto.html)
Update server.pp

Add an optional boolean option ('c2c'): when set to true, the server will enable 'client-to-client' and clients will be able to see each other (https://openvpn.net/index.php/open-source/documentation/howto.html)
Update server.erb

Added support on server.erb template for c2c (client-to-client) option.
Merge pull request #43 from giavac/master

Adds 'client-to-client' option to server configuration