[SJS-251]: Add callback for sendStream

Conflicts:
	publish/skylink.complete.min.js
	publish/skylink.min.js
	publish/skyway.complete.min.js
	publish/skyway.min.js
[SJS-251][ENH]:
- leaveRoom to use Object.keys to count connections
- Add doc

Conflicts:
	publish/skylink.complete.min.js
	publish/skylink.min.js
	publish/skyway.complete.min.js
	publish/skyway.min.js
[SJS-251][ENH]: Revoke fireAlways to prevent callbacks from being accumulated

Conflicts:
	publish/skylink.complete.min.js
	publish/skylink.min.js
	publish/skyway.complete.min.js
	publish/skyway.min.js
[SJS-251]:
- Add test for sendStream callback
- Add condition check to avoid resolution undefined

Conflicts:
	publish/skylink.complete.min.js
	publish/skylink.min.js
	publish/skyway.complete.min.js
	publish/skyway.min.js
[DOC]: Add doc for sdp test
Merge pull request #44 from Temasys/callback

Callback