Clarify how to encode parameters in the Python bindings

We got a report form a user that they had trouble with https://zulip.com/api/get-subscriptions, because they tried:

client.get_subscriptions(include_subscribers=True)

and got an exception. The actual way to pass that parameter is:

client.get_subscriptions(dict(include_subscribers=True))

i.e. pass the parameters as a dictionary, rather than as arguments to this function. I think the user was very reasonable in being confused by this, since we don’t say clearly anywhere on that page how to encode that detail in the Python bindings.

We should figure out how to either document this or adjust API endpoints like this one to pass their kwards are parameters.

[andersk]

Use the same rule the dict function itself uses, which is that the kwargs take precedence:

>>> dict({"include_subscribers": False}, include_subscribers=True)
{'include_subscribers': True}

And we can just deprecate the non-kwargs way, since it can be replaced with client.list_subscriptions(**some_dict).

[neiljp]

As long as there’s no conflict between the specific request parameters and the general options, this seems reasonable to allow, though we’d have to resolve (or document) the case of which takes precedence if specifying parameters both ways.