derandomize setting option not documented

[cdeil]

With full-text search I found that hypothesis has a derandomize setting option:
http://hypothesis.readthedocs.io/en/latest/search.html?q=derandomize&check_keywords=yes&area=default

Can you please update your docs build so that it shows up here?
At http://hypothesis.readthedocs.io/en/latest/settings.html

Also: would it be hard to check that the user passes a bool? Currently this doesn't generate an error, but it would be nice to users if it did, no?

>>> from hypothesis import settings
>>> settings(derandomize='spam')