Useful undocumented parameter for :user/lists/memberships -> filter_to_owned_lists

[Orian Marx (@orian)]

You can efficiently determine which lists owned by the authenticating
user have a target user as a member by adding the parameter
"filter_to_owned_lists=true" to :user/lists/memberships.

This should probably be included in the documentation here:
http://dev.twitter.com/doc/get/:user/lists/memberships