updated for the updated spree 2.2

added to_s to the Json.parse
added "test connection" to show page the button class seems to not exists in the new version
changes for updated spree
added a function call compute amount

the change to the spree backend has added some changes in the adjustment work flow from the adjustments table change to the compute amount
sending tax to rest service using  spree 2.2

the updated spree workflow this current code base will handle updated spree backend.  Need to make sure that the default stock location is populated