Support for java.util.ResourceBundle

First, we love Flogger in our project and use it with standard Java logging.

What would be really cool is, if you could add overloads to the log methods, where you can use a java.utilResourceBundle as first and a bundle key as second argument, as the ResourceBundle key lookup should itself be skipped in case the log level is not enabled. Wrapping each log statement with a guard is possible, but defeats the beauty of Flogger log statements.

Keep up with the great work!