Improve docs to reflect changes from PYTHON-569 and give clear example mod_wsgi configurations:

http://api.mongodb.org/python/current/faq.html#does-pymongo-work-with-mod-wsgi

Bonus: Ask Gentoo to update PyMongo's ebuild to compile the C extension regardless of whether the mod_wsgi use-flag is set. (Remove mod_wsgi from the IUSE list.)