Handle interruptions of work that are not failures
Merge pull request #164 from guidow/non_failure_task_interruptions

Handle interruptions of work that are not failures
Fail assignment if child process failed to start
Deal with process transport not existing
Deal with processes being gone when killing them
Cosmetic: Add two empty lines for readability
Make checking for self.transport more explicit
Merge pull request #166 from guidow/handle_process_start_failure

Fail assignment if child process failed to start
Merge branch 'master' of github.com:pyfarm/pyfarm-agent into nosetests_integration