Switch to using pry-byebug

Pry-debugger fails to install on my machine, where byebug does not. Byebug provides the same features.
Fallback to state_name if state association does not exist

Fixes #11
Don't update last_pushed_timestamps in find_by_batches loop as causes lost updates.

Fixes #9
Order#token => Order#guest_token in Spree 2.3.x
Merge branch 'byebug' of https://github.com/spree/spree_wombat into 2-3-stable
validate response from wombat when pushing objects

Closes #15
Available on may be nil so prevent undefined method on nil error.
Reject id attribute as it should be set by databases primary key.
fix taxon serializing on the products.
Sanitize image url
add spec for add_product with only option hash on variants
Drop order decorator / after commit shipment updates

This was still causing infinite loops via Wombat as everytime a shipment
is updated an order is updated as well which in turn will update the
shipment timestamp again and it will keep getting pushed to Wombat
forever ..
Tweak gemfile for easier bundling and postgres

Without coffee and sass I was getting version conflicts with spree
backend
Fix couple product handler specs
Serialize payment source data.

Specs added for SourceSerializer.

Fixes #17
Example setup should default to filtering complete orders.
Make sure we set the provided shipment id from the payload received as the shipment number
Fix shipment handler spec.
Send discount adjustment.
Order#adjustment_total really means discount total.

Conflicts:
	spec/serializers/spree/hub/order_serializer_spec.rb