auto usage message

[greenkey]

Hi, I'm very new to GO and I think this is the most complete library for the configuration in go.

I would suggest to make a smarter default usage message, maybe taken from the variables needed and with a message like "you can set variables using environment or a json config file (config.json)". The message could be based on the settings provided in the code.

What do you think about?

[LouAdrien]

+1

[paked]

@LouAdrien: would you be interested in working on this?

[paked]

I'd of course be happy to support and review code as needed.

[LouAdrien]

I'd be happy to contribute, but considering the current solution that was chosen, it would be hard to do it without implying a breaking change. I.e currently once the conf.String/Int/Bool is used, the information in the scope of the config object is lost (we could make some global messages, but could not ensure which options was assigned to which object)