Move relationships support to branch `relationships

Closes #4
Static helper to get a MongoCollection
Make tests way more robust
Improve default serialization of objects

Serialize MongoIds and MongoDates by default
Add offsetGet method from Collection
Allow chaining of methods on a model instance

This allows you to do per example `$user->update(array())` instead of `User::update($user->id, array())`
Don't know if that's cool with you, otherwise tell me, sounded logic in my head.
Revert until cause of callStatic regression is found
Model: property setter. No persistence involved here.
In certain cases, we need to access the original MongoCursor

@Anahkiasen For example to iterate through it, without loading
everything into memory at once.
Make MongovelDB a Facade, so that we can dynamically change connection data
Ooops
Ooops (2)
Use a custom static container instead of Laravel's
Implement findOneOrFail (throws a ModelNotFoundException)
Implement a getDatabaseDSN helper
Model implements ArrayableInterface
Merge pull request #6 from arthurdarcet/master

Make Model implements ArrayableInterface
Fix compatibility with latest Laravel
Full text search helper for Mongo 2.4
Bugfix