Set up UINavigationController
Add new view for item details
Set up detail view controller's UI and connections
Push view controller when row selected
Pass data to detail view and display
Save changes in detail view and reload items list
Set title in ItemsViewController
Override setter for item to also set title
Style detail view for iPhone6
Use bar button to create new item
Use bar button to edit items
Fix comments
Remove the now-unnecessary header view

Since we now use bar button items instead.
[Challenge] Display number pad for value field
[Challenge] Dismiss key pads by clicking background

This solves problem of number pad having no return key.