def make_query_string(params)
      clean_params(params).collect do |k, v|
        CGI.escape(k) + '=' + CGI.escape(v)
      end.join('&')
    end
def make_query_string(params)
      clean_params(params).collect do |k, v|
        CGI.escape(k) + '=' + CGI.escape(v)
      end.join('&')
    end
Convert params to query string

 @param [Hash] params
   API call arguments
 @return [String]