Update index.html
Update index.html

Replaced the unversioned CDN (which points to 3.6.4) with the unminified "dev" version which always points to the latest version. Added comments to replace before pushing to production env.
pubnub/webrtc,stephenlb/webrtc-sdk,arielgk/webrtc-sdk,arielgk/webrtc-sdk,PrincessMelime/webtest.io,stephenlb/webrtc-sdk,PrincessMelime/webtest.io,PrincessMelime/webtest.io,stephenlb/webrtc-sdk,pubnub/webrtc,arielgk/webrtc-sdk,pubnub/webrtc