Issue with Exercise 1

Following along with exercise 1, when traversing the snapshot retainers, there is not an obvious `_data` property to be found which could be used to discover the problem. I'm not sure if the issue is because of changes to Chrome or changes to Ember, but the only way to find the source of the memory leak is to look at the module's application code directly. Although the container is retained in memory, there is no way to discover the source from what is presented in the heap snapshot.

Start by reproducing Exercise 1 and traversing the heap snapshot retainers, checking whether the expected _data property appears. Compare the snapshot with the module's application code and determine whether the exercise or its explanation needs updating; done means the leak source is discoverable as intended or the limitation is clearly documented.

Written by the indexing model from the issue text.