Pass $maxDistance in $near object as described in docs

Hey Aaron,

I'm going through cleaning up 2.6-specific failures in mongoose and ran into this rather unfortunate one that also affects mquery. This works against 2.4.10 and prevents 2.6.0 from returning a nasty `Can't canonicalize query: BadValue geo near accepts just one argument when querying for a GeoJSON point. Extra field found: $maxDistance: 1000000` error. See http://docs.mongodb.org/manual/reference/operator/query/near/ for docs.

Also, may make sense to give me push / publish access to mquery.

Cheers,
Val