add SimpleStreamResponseSender
added file and class headers
added abstract response sender

send Headers not uses "headers_sent()" directly
added get/setEvent method in SendResponseListener
added unit test for send response listener
optimized SendResponseEvent
added ConsoleResponseSenderTest
added SendResponseEventTest
added phpenrivonment response sender test
improved console response sender test
fixes in SimpleStreamResponseSender
added tests
added priority description to method docblock
added additional test
trying to send the headers multiple times results in headers only being sent once
optimize AbstractResponseSender
Merge branch 'streamresponsesender' of git://github.com/prolic/zf2 into feature/3343
[#3343] CS and test fixes

- Minor CS fixes
- Moved code from conditionals into method body where possible
- Fixed AbstractResponseSenderTest to account for xdebug headers, if present
Merge branch 'feature/3343' into develop

Close #3343