* Add BrokerConnection.send_pending_requests to support async network sends
* Send network requests during KafkaClient.poll() rather than in KafkaClient.send()
* Dont acquire lock during KafkaClient.send if node is connected / ready
* Move all network connection IO into KafkaClient.poll()

In an effort to reduce the surface area of lock coordination, and thereby hopefully reduce lock contention, I think we can remove locking from the read-only KafkaClient methods: connected, is_disconnected, in_flight_request_count, and least_loaded_node . Given that the read data could change after the lock is released but before the caller uses it, the value of acquiring a lock here does not seem high to me.

Since 1.3b1 (released Oct 10, 2014) Sphinx has support for NumPy and
Google style docstring support via sphinx.ext.napoleon extension.
The latter is already used, but sphinxcontrib-napoleon requirement
still presents.

Signed-off-by: Stanislav Levin <slev@altlinux.org>

The problem is that the type of required operation result is
"long".

```
>>> type(278251978 & 0xffffffff)
<type 'long'>
```

However, by default "format" method uses __format__():

```
>>> (278251978 & 0xffffffff).__format__('')
'278251978'
```

So, let's compare things using the same engine:

```
>>> "{!r}".format(278251978 & 0xffffffff)
'278251978L'
```

Fixes: https://github.com/dpkp/kafka-python/issues/1717
Signed-off-by: Stanislav Levin <slev@altlinux.org>