logger disabled by default in v1+; add option to enable logger?

[betalantz]

I've been looking for a way to config json-server to re-enable the logger from versions < v1. It's very useful to see a log of processed requests. Looking at the source code, I think I see the boolean to enable it, but it's currently hardcoded false. Could there be an option flag "-l", "--log" or some other way to enable it from the command line? Thank you.

[kaz1ngton]

Opened a pull request