activating flying saucer logging

I had a "semicolon moment" where I was digging deep in this plugin and flying saucer only to eventually discover my css was missing a semicolon, which was causing the parser to just drop the css. The way I finally discovered this small bug in my code, was by enabling logging in flying saucer. 

I have added a note on how to provide system property to activate logging within flying saucer. flying saucer. Could have done it programmatically in the code with something like if (log.debugEnabled) System.setProperty... .

For some reason, the logging does seem to happen until the second time a
document is rendered. Still very useful though!