add REPL completion for resource

[Jefftree]

Added iPython tab completion for client resource.

client = SwaggerClient.from_url('http://petstore.swagger.io/v2/swagger.json')
wrapped_client = ZipkinClientDecorator(client)

After typing wrapped_client.pet.<TAB>

Before: Completes with with_headers which is technically a private decorator function. We had to use wrapped_client.pet.resource.<TAB> to obtain the list of swagger operations. This was due to the fact that __getattr__ was set, but __dir__ was not set.

After: Completes with .addPet, .getPetById, etc. These are the functions we want to expose.

Testing

make test passes and also manually tested with a SwaggerClient.

[kaisen]

nice! 🚢

[bplotnick]

Yes! This fixes such an annoyance.