+ Remove open("/proc/net/tcpprobe") and corresponding readline() (it can block when there's nothing to read). select.select(), etc,... don't seem to work on /proc.
	+ Using subprocess with "head" and subprocess.communicate(TIMEOUT) to read a line now

+ fixed ipv4 compatibility bug (should work now, but why u no use ipv6?)

+ added delayed/early_stop senders. You can now specify a time in seconds that a sender gets delayed before sending, and a time in seconds that the sender is stopped early. Each sender will run for <global test length> - <start
delay> - <early stop> seconds.

+ start_time was incorrect
+ Popen.wait() buggy with multiprocessing

- code restructuring