loadDatabase not working

Hi @raix

I am using groundDb in an exiting application.
Right now I am simply trying to ground `Meteor.users`:

```coffeescript
GroundedUsers = new Ground.Collection("Meteor.users")
GroundedUsers.observeSource(Meteor.users.find())
if Meteor.isCordova && Meteor.status() != 'connected'
GroundedUsers.loadDatabase()
```

The above did not work.
So, I tried overriding `find` and `findOne` method:

```coffeescript
Meteor.users.find = (args...) ->
GroundedUsers.find(args...)
Meteor.users.findOne = (args...) ->
GroundedUsers.findOne(args...)
```

Now, `Meteor.users.find({_id: Meteor.userId()}).fetch()` should return a document but it returns a plain object. I have apply `Collection._transform` to transform it into a document.

If `loadDatabase()` would be working, I should not have to do the same.

PS: Above code is written in [coffeescript](http://coffeescript.org/).

Any help would be nice.

Thanks

Start by tracing Ground.Collection.loadDatabase() and how GroundedUsers.observeSource(Meteor.users.find()) populates the local collection. Reproduce the offline Meteor.users case from the issue, then compare the returned object with the expected transformed document; done means loadDatabase works without overriding find or findOne.

Written by the indexing model from the issue text.