Allow to change/turn off CachedResource for some actions, by specifing .cache option

Usage example:
```coffee
PaymentResource = $cachedResource 'payments', 'payments/:id', {id: '@id'},
  charge:
    method: "POST"
    cache: false
```

I want to have methods `get` and `save` still cached by $cachedResource, but I'd want to disable caching for `charge` / `$charge` method, because f.e. I don't want this request to be repeated by CachedResource in the background.

Note: This is more like feature request. Don't merge this PR yet - my implementation isn't fully working yet.