Testing: turn examples into integration tests

[backkem]

Turn examples into integration tests.

Design goals:

• Use the existing examples
• Have minimal impact on the example code E.g.: add event listeners on the existing textareas.
• Use go test to run the tests
• Place integration tests behind a build flag to avoid bloating unit tests (E.g.: go test github.com/pions/webrtc -tags=integration)
• Communicate test data/results over http in order to minimize use of specialized APIs for test subjects (like a browser, node, ...).

(Moved from #120)

[netwer]

@backkem you did not implement the turn server yet?

[backkem]

There is a turn server at pions/turn but we didn't implement connecting to a TURN server from pions/webrtc yet. (Note that this ticket doesn't relate to TURN)

[Sean-Der]

Moved to https://github.com/pion/webrtc/wiki/Big-Ideas

I think this is a great idea, but I don't see it moving anytime soon unfortunately :(