Allow the test server to initialize without routes.

Added an optional parameter to the test server which will enable/disable
setting the routes for tests. The default is `true` or enabled.

This will be useful for testing passing arguments to the various route
handlers.
Added 'beforeSave' functionality.

Per the discussion on [Issue
8](https://github.com/saintedlama/restify-mongoose/issues/8) this is the
functionality to execute a custom function before the model is saved.
This allows for operations such as inserting a user id on a model before
is it saved.