Support of changed behavior of event_traits.

Before cocaine::io::event_traits<Event>::result_type was mpl::list for events with result_type specified as mpl::list, but now it's std::tuple. So framework didn't unpack result to pass it to the handler. Now it's fixed.
Merge branch 'service_handling_fix'

Conflicts:
	include/cocaine/framework/service.hpp
Changelog bump - 0.10.4-2.