Updated KafkaClient API - version 0.9.0

# Problem
kafka-python updated the latest `__init__` api to use comma delimited host string, this breaks the old api which was used in the check; on the bright side it simplifies the checks code.

info dump
```
    kafka_consumer
    --------------
      - instance #0 [ERROR]: TypeError("object of type 'int' has no len()",)
      - Collected 0 metrics, 0 events & 0 service checks
```

Stack Trace:
```
2014-07-10 18:05:38 UTC | INFO | dd.collector | kazoo.client(connection.py:536) | Closing connection to ec2-54-191-60-165.us-west-2.compute.amazonaws.com:2181
2014-07-10 18:05:38 UTC | INFO | dd.collector | kazoo.client(client.py:439) | Zookeeper session lost, state: CLOSED
2014-07-10 18:05:38 UTC | ERROR | dd.collector | checks.kafka_consumer(__init__.py:507) | Check 'kafka_consumer' instance #0 failed
Traceback (most recent call last):
  File "/usr/share/datadog/agent/checks/__init__.py", line 498, in run
    self.check(copy.deepcopy(instance))
  File "/usr/share/datadog/agent/checks.d/kafka_consumer.py", line 71, in check
    # Connect to Kafka
  File "/usr/local/lib/python2.7/dist-packages/kafka/client.py", line 40, in __init__
    self.load_metadata_for_topics()  # bootstrap with all metadata
  File "/usr/local/lib/python2.7/dist-packages/kafka/client.py", line 252, in load_metadata_for_topics
    request_id, topics)
  File "/usr/local/lib/python2.7/dist-packages/kafka/protocol.py", line 354, in encode_metadata_request
    KafkaProtocol.METADATA_KEY)
  File "/usr/local/lib/python2.7/dist-packages/kafka/protocol.py", line 49, in _encode_message_header
    return struct.pack('>hhih%ds' % len(client_id),
TypeError: object of type 'int' has no len()
```

# Tests
*Note: there we no tests to update so I did not bother writting one*

- [x] Updated local agent, restart and saw the follow under info:
```
    kafka_consumer
    --------------
      - instance #0 [OK]
      - Collected 8 metrics, 0 events & 0 service checks
```

# Reading Material
[kafka-python docs](https://github.com/mumrah/kafka-python#high-level)
[kafka-python KafkaClient.\__init__](https://github.com/mumrah/kafka-python/blob/master/kafka/conn.py#L16)
[kafka-python collect_hosts](https://github.com/mumrah/kafka-python/blob/master/kafka/conn.py#L16)