title: Include WebRTC in iOS project
body: <p>I trying to deal with the AppRTCDemo projet but I am getting error.
  Which library I forget to include ?</p>
  
  <p>Log error : </p>
  
  <p><code>Undefined symbols for architecture armv7s:
    "_OBJC_CLASS_$_RTCVideoRenderer", referenced from:
        objc-class-ref in VideoView.o
    "_OBJC_CLASS_$_RTCSessionDescription", referenced from:
        objc-class-ref in AppDelegate.o
    "_OBJC_CLASS_$_RTCICECandidate", referenced from:
        objc-class-ref in AppDelegate.o
    "_OBJC_CLASS_$_RTCVideoCapturer", referenced from:
        objc-class-ref in AppDelegate.o
    "_OBJC_CLASS_$_RTCPair", referenced from:
        objc-class-ref in AppDelegate.o
    "_OBJC_CLASS_$_RTCMediaConstraints", referenced from:
        objc-class-ref in AppDelegate.o
    "_OBJC_CLASS_$_RTCPeerConnectionFactory", referenced from:
        objc-class-ref in AppDelegate.o
    "_OBJC_CLASS_$_RTCICEServer", referenced from:
        objc-class-ref in APPRTCAppClient.o
  ld: symbol(s) not found for architecture armv7s
  clang: error: linker command failed with exit code 1 (use -v to see invocation)</code></p>
  
  <p>Thanks</p>