fakemongo/fongo — pull request #81 by libetl (2014-12-31 12:49:46+00:00)
Title: Positional item update does not work with a $elemMatch query

This case happened in my project. The update command looks like this :
db.coll.update ({"foo" : {$elemMatch : {"bar" : "john", "foobar": "doe"}}, {$set : {"foo.$.foobar":"doe2"}})

It works in mongoDB but does not work in fongoDB.
I fixed it in your source code, and added a unit test.