Individual levels for multi handler

[claytoncasey01]

It would be nice when using the multi handler if we could set the individual logging level for each handler. For example in my application I only want info to be logged to the cli and Warn, Error, and Fatal to be written out as json to a file.

Based on an initial look this might require a lot of changes since Level is currently part of the Logger struct.

[tj]

Agreed, I'd like if Logger/Entry had more parity, might have to be a v2 thing