simplify method missing
change Keys#to_mongo() to take a hash of options; add option :include_all_keys which will return nullified keys
Fix bug in partial update code.  Make sure when partial updates are off, null values properly get propagated on updates

(this bug pops up because to_mongo doesn't return the full hash - it excludes null keys)
turn off partial updates
Add attributes(:all_keys => true) to return non-nil keys
update ChangeLog