code: def external_session_url(email, chrome, url, integrator_id, client_id)
        options = { :body => {
          :Email => email,
          :Chrome => chrome,
          :Url => url,
          :IntegratorID => integrator_id,
          :ClientID => client_id }.to_json }
        response = put("/externalsession.json", options)
        Hashie::Mash.new(response)
      end
docs: Get a URL which initiates a new external session for the user with the
   given email.
   Full details: http://www.campaignmonitor.com/api/account/#single_sign_on
  
   email         - The email address of the Campaign Monitor user for whom
                   the login session should be created.
   chrome        - Which 'chrome' to display - Must be either "all",
                   "tabs", or "none".
   url           - The URL to display once logged in. e.g. "/subscribers/"
   integrator_id - The integrator ID. You need to contact Campaign Monitor
                   support to get an integrator ID.
   client_id     - The Client ID of the client which should be active once
                   logged in to the Campaign Monitor account.
  
   Returns An object containing a single field SessionUrl which represents
   the URL to initiate the external Campaign Monitor session.