def request_xml
      request_params = @params.dup
      token = request_params.delete("token")
      xml = ""
      request_params.each do |key, value|
        xml << "<var name=\"#{escape(key)}\" value=\"#{escape(value)}\"/>"
      end
      "<sessions><token>#{token}</token>#{xml}</sessions>"
    end
def request_xml
      request_params = @params.dup
      token = request_params.delete("token")
      xml = ""
      request_params.each do |key, value|
        xml << "<var name=\"#{escape(key)}\" value=\"#{escape(value)}\"/>"
      end
      "<sessions><token>#{token}</token>#{xml}</sessions>"
    end
Generates xml suitable for an XML POST request to Tropo

 Example:
   tropo_message = Tropo::Message.new
   tropo_message.to = "44122782474"
   tropo_message.text = "Hi John, how r u today?"
   tropo_message.token = "1234512345"

   tropo_message.request_xml # =>
   # <sessions>
   #   <token>1234512345</token>
   #   <var name="to" value="44122782474"/>
   #   <var name="text" value="Hi+John%2C+how+r+u+today%3F"/>
   # </sessions>"