Show some info after start daemon mode

[PennyQ]

@maxwelltsai Currently there is no output after starting daemon mode, although user could switch to interactive mode or check the log file to see if daemon is running, while it could be more 'direct' and convenient to put a brief info or even a progress bar.

[PennyQ]

Already implemented with some msg when typing simon start/stop twice, as below

➜  SiMon git:(rm_unnecessary_files) ✗ simon start
➜  SiMon git:(rm_unnecessary_files) ✗ simon start
Error: the SiMon daemon is already running with process ID: 9125
Please make sure that you stop the daemon before starting it. Exiting...

An ideal way is to give a msg at first sight of typing simon start/stop with PID.