Incorrect marshalling of boolean query params

[aviskase]

Take for example this param:

"parameters": [
          {
            "name": "force",
            "type": "boolean",
            "in": "query"
          }
]

Currently when bravado-core tries to marshal this param, it just casts it to str() which leads to True/False instead of true/false

Temporary ugly monkeypatch snippet for those, who use bravado+pytest:

from bravado_core.param import marshal_param

def _marshal_param(param, value, request):
    marshal_param(param, value, request)
    if param.name in request['params'] and type(value) is bool:
        value = str(value).lower()
        request['params'][param.name] = value

monkeypatch.setattr('bravado.client.marshal_param', _marshal_param)

[frankandrobot]

How would you apply the monkeypatch w/o the monkeypatch test fixture?