create_param_docstring doesn't dereference $ref properly

[jakul]

I have a working Open API, which bravado gives the docstring below for. The param_spec which gets passed in is listed below that. create_param_docstring doesn't know how to dereference $ref'd parameters, and so gives an incorrect docstring.

In [3]: client.Users.user_action_elasticsearch?
{'x-scope': ['http://localhost:5010/users/swagger.json'], u'$ref': u'#/parameters/body_action_user_elasticsearch'}
{'x-scope': ['http://localhost:5010/users/swagger.json'], u'$ref': u'#/parameters/scroll'}
Signature:       client.Users.user_action_elasticsearch(self, **op_kwargs)
Call signature:  client.Users.user_action_elasticsearch(**op_kwargs)
Type:            CallableOperation
String form:     <bravado.client.CallableOperation object at 0x10f260d50>
File:            ~/.virtualenvs/service-intel/lib/python2.7/site-packages/bravado/client.py
Docstring:
[POST] Search Elasticsearch

This view is a direct passthrough to the Elasticsearch `_search` endpoint. Search syntax and examples can be found at https://www.elastic.co/guide/en/elasticsearch/reference/5.1/search-request-body.html

:param None: Document your spec, yo! (optional)
:type None: None
:param None: Document your spec, yo! (optional)
:type None: None
:returns: 200: Search response
:rtype: object
Class docstring:
Wraps an operation to make it callable and provides a docstring. Calling
the operation uses the configured http_client.

:type operation: :class:`bravado_core.operation.Operation`
Call docstring:
Invoke the actual HTTP request and return a future.

:rtype: :class:`bravado.http_future.HTTPFuture

{'x-scope': ['http://localhost:5010/users/swagger.json'], u'$ref': u'#/parameters/body_action_user_elasticsearch'}
{'x-scope': ['http://localhost:5010/users/swagger.json'], u'$ref': u'#/parameters/scroll'}