Fallback to state_name if state association does not exist

Fixes #11
fallback to use the state_name when state can't be found

Closes #12 #14
Make sure we set the provided shipment id from the payload received as the shipment number

Conflicts:
	lib/spree/wombat/handler/add_shipment_handler.rb
	spec/lib/spree/wombat/handler/add_shipment_handler_spec.rb
Update debuggers
Adding shipping_instructions to order serialization
Fixes #32
Fix shipping instructions.
Fix specs.
Merge pull request #35 from spree/responder-objects

Improves Spree::Wombat::Response serializer to handle objects
Conflicts:
	spec/serializers/spree/wombat/responder_serializer_spec.rb
add discount key to adjustments
Fix double constantize bug.
Update wombat client to validate wombat response.
Allow configuration of batch size.
always return the master variant in the variants key when serializing products

Conflicts:
	spec/serializers/spree/wombat/product_serializer_spec.rb
Add handlers exception logging to Rails log
Fixes #42
Fixes #44