I'm gonna need a write up. I've been looking at the code for 10 or 15 minutes and I still haven't found "fizz", "buzz", or the number 100 anywhere in the code. It's amazing.
I think it’s really shortsighted to hardcode them statically into constants. You’d have to build a completely new binary should the requirements someday change! Obviously they belong behind a configuration interface, an instance of which can then be dependency injected to places that need them. In this way you can easily supply them from whatever source you like, such as a properties file, XML document, a database or even a web service.