Fixed `<GhMemberAvatar>` expecting an EmberObject object
Fixed `<GhMemberAvatar>` expecting an EmberObject object

no issue

- it should be possible to pass a POJO rather than an EmberObject object so the component is usable with raw data like we have with member events
- switched to using `get()` rather than assuming the passed in object has it's own `.get()` method

TryGhost/Ghost-Admin,TryGhost/Ghost-Admin