Seldaek/log — pull request #2 by theunraveler (2012-12-13 17:05:25+00:00)
Title: Adding AbstractLogger implementation, moving NullLogger to subclass

As per [this thread](https://groups.google.com/d/msg/php-fig/r85O6ucEBWE/wOCJpd2m4ysJ), I'm adding an `AbstractLogger` class.

Another added beneit of having this is that `NullLogger` can inherit from it and become even simpler :-)