Read post body

Parses arguments form body of POST request and sends them to the specified cgi script.

NOTE: cpp-server only supports cgi scripts written in PHP and Pearl, and they are required to be located in the `cgi-bin` directory. Arguments are accepted from the client as a string of variables separated by the '&' symbol, and are sent to the specified CGI script as space-delimited command line arguments.

fixes #28

@smurray47, @julienmansier any thoughts on the completeness of this method?