Create a PySide GUI window.
Make app more OOish
Make MainApp a QTreeView
Add stubby data model
Fix DataModel.headerData()
Add DataModel.flags()
Minor formatting change
Add hardcoded data table behind model
Add simple DataItem class
Display header from DataItem root
Init data with arrays, not tuples
Set ItemIsEditable flag to true
Implement setData
Implement columnCount
Add third column

Just to test that the TreeView displays everything.
Minor: Fix line wrapping
Extract dummy data injection out of DataModel
Extract temp root for readability
Attempt to add child of child

This currently blows up. Let's fix it!
rowCount returns numChildren for valid parent