Add is_failed/2 with additional argument to check subelement with backwards compatibility for is_failed/1
dropped is_failed/1
Merge pull request #23 from sinkovsky/is_failed_with_subelement_pred

Add is_failed/2 with backward compatibility
Escalus_tcp now handles stream management book-keeping (acks) transparently
merge get_sm_h/1 export

Conflicts:
	src/escalus_tcp.erl