Hi Richard,
as commented above FF 47.0 came with a bug causing Selenium to stop working, that's the reason we have stablished FF 46.0.1 like the latest working combination.
Coincidently, yesterday, Selenium released 2.53.1 that comes with a new selenium-firefox driver, ready to work with the, also new, FF 47.0.1
For the records we are testing that combination (Selenium 2.53.1 + FF 47.0.1) right now @ MDL-55094 . If it's probed to work and doesn't break any other browser... we'll add it as a working combination to the Docs, so everybody knows which ones are supported.
I really would recommend people to stay sticky to those combinations, because it's really hard to verify each one, and along the last year it has been a nightmare to keep things working, with every update of Selenium or Firefox causing new problems. That's pretty much the reason we decided to create that list of working combinations.
Ciao