Verbose log of workers

[sio4]

Hi,
Today I tried to use the simple worker. and I found the log level for "Performing" (worker/simple.go#L75) and "Completed" (worker/simple.go#L89) is Info. I think it can be Debug level because this logs need to be suppressed when I put this app in production.

[markbates]

A PR would be welcome for this.

[sio4]

OK, I will do this tonight.

[sio4]

I removed two of my own comments because it's my fault.
I just made simple changes on current development branch and requested a PR.

[sio4]

Thanks for merging it quickly. I hope it will get on the master soon.
Thanks.

[markbates]

Thank you! The next release is coming up soon. So it won't be a long wait. :)