apprtc: add &ssr=1 for stereoscopic render (e.g. Oculus Rift).
(local preview during the call is removed in this mode)

Remember to double-click the remote view canvas to full-screen it!
Merge pull request #31 from GoogleChrome/fischman-stereoscopic

apprtc: add &ssr=1 for stereoscopic render (e.g. Oculus Rift).