[5.2] Added support for different log levels.

[melanholly]

This adds support for different logging levels that seems to be implemented but it was missing from this file. Now we can use different logging levels. If we switch from development to production we have different amount of logging information.

This is feature of Monolog and it was added in src/Illuminate/Log/Writer.php but not in src/Illuminate/Foundation/Bootstrap/ConfigureLogging.php

This functionality is not tested since it is part of Monolog.

[GrahamCampbell]

I don't think this needs to go in the core. 👎 from me. I also would suggest a better way of doing it: https://github.com/AltThree/Logger.

[melanholly]

OK so you suggest that I use different logging package if I have to use different log levels beside debug?
Well I just wanted to extend the support for Monolog so we can have different log levels for different environments.
Please close the issue if you think it shouldn't be in the core.