mean and floatify methods, plus bug fix in BitFloor class



* Delete duplicate `BitFloor.book()` method
* `lib.fencebot.floatify()` recursively walks a dict, list or other object, converting any values it can into floats (great for the output of `BitFloor.book()`)
* `lib.fencebot.mean()`
* `lib.fencebot.__main__()` just loops continuously displaying the floatified and centroided book, runs from local folder without environment change
* enable argless script running (default config hard-coded)

TODO:
eliminate do-nothing json_ascii.py module or calls