added ability to include arbitrary log4j settings

I want to pipe all my logs to logstash through the log4j [socket server] (http://howtodoinjava.com/2013/04/08/log4j-socketappender-and-socket-server-example/) so i need the ability to add or customise settings. I dont want to put logic in the template, so I am adding this through custom attributes.
Never update version number in a pull request. It's up to the maintainer to decide when to do it and what the next version should be.