Name change to Backbone.Model.Plus. Seems more scaleable than
Backbone.This.And.That.And.Oh.This.One.Other.Thing.Too

Updated package, component, etc.
Also replacing @asciidisco's name with my own in tests and such.
Clean up a little lint
Ensure that attempts to read a nested property of a null parent (e.g. get('user.address.city') when
user.address doesn't exist) returns undefined rather than exploding.

Also found that mutator setters always create a property of the same name in the attributes object.
Therefore this needs to be actively deleted (not just ignored) if the property is mutator is marked
transient.