Items return from Item.all() SKU property always None

[dangurland]

Steps to Reproduce:

1. Set SKU property on any Products and Services object
2. Execute Item.all()
3. SKU property is None for all returned objects in Item list

[laf-rge]

Created a PR to address the issue. Looks like the API doesn't retrieve that by default. Worth a discussion if we should always do this or make this configurable, but for now, this will always retrieve them on Item.

[anoteboom]

I see in this PR an issue with trailing slashes is fixed. We are looking forward for this fix.

[ej2]

Fixed in 0.9.12