Signature Support

[CharlesBergmeier]

Your python library doesn't currently support sending a signature argument for newly created packages. The following change is needed:

Under the Shipment class, the class method create currently has the following signature:

def create(cls, to, packages, service, from_=None, carrier=None, reference=None, options=None, label=None):

Update this to:

def create(cls, to, packages, service, from_=None, carrier=None, reference=None, options=None, label=None, signature=None):

And then within the class method, add these lines:

if signature:
  shipment._data['signature'] = signature

Let me know if there is another way to send that argument in the existing library that I missed. Thanks!