Fix constructor doc (#321)

[rnpridgeon]

No description provided.

[edenhill]

The kwargs isn't very helpful without an explanation, so I suggest you remove them.

Also, add a param stanza for the config, saying something like: :param dict config: Configuration properties

[rnpridgeon]

So silently accept kwargs then without advertising this capability in the docs? Is that the right move or perhaps a brief description linking the rdkafka configuration page

[edenhill]

we should link to CONFIGURATION.md, but that is for the config dict.
The kwargs is really just an alternative to the dict, it takes the same keys (but none of the standard config properties will work since they contain dots . ).

You can do this:
p = Producer({"bootstrap.servers":"gnägg"}, logger=mylogger)
which is identical to:
p = Producer({"bootstrap.servers":"gnägg", "logger": mylogger})

so I don't think there is any need to expose kwargs.

[rnpridgeon]

To encourage good behavior perhaps its a good idea to expose kwargs referencing the configs specific to the python binding in the docs

default.topic.config as I understand it is on its way out anyway :)

[rnpridgeon]

There are some extra formatting changes to appease the sphinx gods

[edenhill]

LGTM