Expandable feedback not working

[chrisgriffith]

Short description of the problem:

Buttons that are marked as expandable are not filling the created gap with their assigned color

What behavior are you expecting?

As the user performs a full swipe gesture the button's width should grow to fill in the space.

Steps to reproduce:

1. Create new Ionic v2 (rc0) blank starter
2. Replace the default content with the sample code from http://ionicframework.com/docs/v2/api/components/item/ItemOptions/
3. Wrap it in
4. Run.

The item row itself responds to the expansion, just not the button.