log format in env.py

[wangjunxiao]

log format in env.py should not be 'YY-MM-DD_HH:MM:SS', which cannot create log file successfully in Windows, because ':' is an invalidated character in Windows file name. Maybe can change it to 'YY-MM-DD_HH-MM-SS'.

[bupt-steven]

I have modify it ,thanks

[bupt-steven]

you can pip install the new lastest code with
pip install LiveStreamingEnv==0.2.7