v0.5.0, 17/05/2014 -- Rewrite of NmapProcess
                    - removed Threads to read stdout/stderr
                    - replaced by Process
                    - use of semaphore to not consume CPU while looping
                    - added NmapTask class
                    - added NmapProcess.current_task
                    - added NmapProcess.tasks list
                    - fixed bug in NmapProcess.state
                    - note NmapProcess.is_alive() is not recommended