A couple bugs in optgroup functionality

[ghost]

Reproduce Optgroup bug one:

1. Expand some option group.
2. Select an option so it sits in the 'selected' list.
3. Collapse the option group.
4. Trash your selected item.

The option group the trashed item belongs to is still collapsed and the item is sitting under it.

Reproduce Optgroup bug two (this is a bug in the example code and not the lib):

1. Expand some option group.
2. Select an option so it sits in the 'selected' list.
3. Collapse the option group.
4. Expand the option group.
5. The 'selected' option reappears in the 'selectable' list but it should not be there.

[ghost]

I thought you could attach code to an existing github issue with a pull request, but I was wrong. This is fixed with the pull request I just sent (issue # 21).

My bad.