Add example with MetaEvent function
Fix php docs for example
Implement CancelMessage
Fix php docs and coding style
Merge origin/master

Conflicts:
	src/Thruway/Call.php
	src/Thruway/Message/ErrorMessage.php
	src/Thruway/Role/Subscriber.php
Fix php docs and coding style after merge code
Merge pull request #39 from oanhnn/master

Fix php docs and coding style