Improve raw expressions on model classes

Adding information about new associate and dissociate methods for emb…

…edsMany relations

Merge pull request mongodb#149 from khamkham/master

Add natural reverse (descending) sort option

Fixes mongodb#147

Merge pull request mongodb#137 from neoxia/master-embeds-many

[Proposal] Add embedsMany relationship to Eloquent Model

Tweaking id accessor for mongodb#108

Fixed insert return type and tweaked some tests

Fix model collection name

Switching to Laravel 4.1

Adding whereRaw test