New Mongoose extension - Mongoose-Joins

[goulash1971]

Hi guys

Following up from our discussion on DBRef support I've pushed another mongoose extension project onto GitHub called (mongoose-joins)[https://github.com/goulash1971/mongoose-joins] that provides some basic (but extensible) pseudo-join support for mongoose.

I'm busy updating the README.md and adding a couple of basic examples - but it's good for a rev1 release if you'd like to add it to your list of extensions.

Cheers
Stuart