Cup 2.1.1 is released

Version 2.1.0 - 2019.2.1 ~ 2019.5.10

[New] cup.net.get_interfaces - Get interfaces of a linux host
[New] cup.res.linux.get_cpu_core_usage - Get cpu core usage
[Enhancement] cup.shell.oper - Md5 hexdigest generation (py3 compatibility)
[New] Py3 compatibility test and reconsutrction is undergoing
[Enhancement] cup.shell.oper - Change subprocess.Pipe(shell=True by default to shell=False)
[Bug] github socket closure (#32)
[Enhancement] cup.shell.oper - Async_run with Popen(shell=True) and with a temp script