Demo of using weak references in RubyMotion

This app is used to demonstrate an example of a memory leak in iOS, and how to fix it using a WeakRef.

There are several labels in the repo that show different stages in the process.

Creates/releases a ToDoItem. The ToDoItem allocates a large array to be able to observe the memory in Xcode Instruments

Adds a notifier to the ToDoItem. In this branch, the notifier does not reference the parent ToDoItem, so there is no change in memory

Now the notifier has a strong reference to the ToDoItem. This creates a memory leak.

The notifier uses a weak reference to store the reference to the parent. This fixes the memory leak.