Typically a vapor barrier is used to prevent migration of water vapor from an area of warmer tempeature to an area of cold where it would condense to liquid. The rule for insullation is "vapor barrier to the warm side". (Think of how we install fiberglass batts.) Water vapor seeks to go from warm to cold. While this doesn't specifically address whether or not a vapor barrier is needed with a rigid foam application, it does justify locating it between the first layer of sheathing and the foam.
A house wrap is intended to keep water and wind infiltration to a minimum. There are some who believe that a properly isnstalled skin (sididng, masonry, etc.) should keep water out and a little bit of air movement behind the skin is not a bad thing, thus they don't believe in using house wraps. The real enemy of an enclosure system is the water vapor that infiltrates it and condenses on the cooler surfaces which then suffer rot and mold. This is akin to having a leak which lets rain in.
I hope this helps clarify.