def post(method, params={}) # :nodoc:
      Response.new Client.post(api_url,
                               :headers => auth,
                               :body => Client.xml_body(method, params))
    end
def post(method, params={}) # :nodoc:
      Response.new Client.post(api_url,
                               :headers => auth,
                               :body => Client.xml_body(method, params))
    end
HTTParty (sort of) assumes global connections to services
 but we can easily avoid that by making an instance method
 that knows account-specific details that calls its
 coresponding class method.
 note: we only need to provide a #post method because the
 FreshBooks API is POST only