Lowers FF requirement to v38.

modules/RTC/RTCUtils.js

     if (navigator.mozGetUserMedia) {
         console.log('This appears to be Firefox');
         var version = parseInt(navigator.userAgent.match(/Firefox\/([0-9]+)\./)[1], 10);
-        if (version >= 39) {
+        if (version >= 38) {
             this.peerconnection = mozRTCPeerConnection;
             this.browser = RTCBrowserType.RTC_BROWSER_FIREFOX;
             this.getUserMedia = navigator.mozGetUserMedia.bind(navigator);