added screed and read_parser streaming testing

Marked as known failing since they currently fail.
Will investigate.
When I run this on the command line with screed 0.7 and 0.7.1 it works. Maybe using a FIFO named pipe (os.mkfifo) like we did when we were debugging with GDB would do the trick. That way you can still invoke the script using utils.runscript like the rest of the tests.