Pod typo, file tests, and a maybe a new file argument

I love this module, but everytime I use it I find myself overwriting the 'new' functionality to be able to specify my own `callbacks` argument for the file logger.
What do you think about making this customizable?

Attached is a very simple solution for doing so.

If you don't care for the option or the implementation,
feel free to use either of the first two commits (pod syntax error and basic file tests).