[BUGFIX beta] Ensure namespaces are cleaned up.

Prior to this change, calls to `Ember.Namespace.byName` would still
return the cached class since it was being saved off to
`Ember.Namespace.NAMESPACES_BY_ID` but not cleared.
minor doc fixes
[BUGFIX beta] More descriptive error when setting read-only property
minor doc UI fixes
[DOC beta] view.nearestOfType() is a method not a property
[DOC beta] Update filterBy docs to show that the value can be any type
[DOCS beta] Mention passing identifiers to `transitionTo`
[BUGFIX beta] Handle ES6 transpiler errors.
[FEATURE ember-routing-auto-location] Prepend location.origin to location.replace attempts
[DOC beta] Fix link to `Ember.ControllerMixin#replaceRoute`
[DOC beta] typo in docs