adding display popup option

Accept if you'd like, a basic copy/paste from the facebook authorizationParams for foursquare to have an optional display type.

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Display Types (https://developer.foursquare.com/overview/auth#display)

By default, foursquare auto-detects the appropriate type of site to display for the auth dialog. You can force a specific display type by adding display=XXX to your authorize or authenticate URLs. The supported display types are touch, wap, and webpopup. We don't recommend specifying a display type, **unless you are using the webpopup display.** In webpopup mode, we pop up a new web window for the auth dialog, redirect to the callback in the caller window, and close the popup window after the user authorizes the app.