[5.3] Added spec and fix for Router implicit binding through IoC

[asutoshpalai]

If a Model has been bound to another one though $this->app->bind('Model1', 'Model2'), the implicit binding for the old model in the controllers still resolves to the old model rather than the one it's bound to.

This fixes it.

[taylorotwell]

Why do you have an Eloquent model aliased to another model name?

[asutoshpalai]

I was building a core Laravel application as a package. This core application is to be used in other applications which should be able to override the features provided by the package.

To allow overriding (extending) the package's Models by the application and use the extended one inside the package, I was using dependency injection and IoC container. It is working everywhere except at implicit model bindings in the controllers.