Added caching support
In an effort to make Iridium the go-to ORM for Node.js applications :wink:
we've implemented inline caching support - allowing you to easily cache
requests for single objects using your favourite caching engine (Redis/Memcache etc.).

As it stands, the cache is only hit for Model.get(_id)/Model.find(_id) and is automatically
updated when inserts and instance specific saves/refreshes/removals are executed.

It doesn't aim to be a be-all and end-all replacement for having a fast MongoDB server,
but it should allow you to offload some of the overhead on common operations to some
kind of KVS which is better suited to the task.
Allow more complex caching designs
Caches are now selected based on whether they report an ability to cache the given
document's selection conditions. This should allow more flexible usage of caches
in real world applications (where you won't necessarily be using _id the whole time)