A simpler kafka consumer

```
kafka = KafkaConsumer('topic1')
for m in kafka:
    print m

kafka = KafkaConsumer('topic1', 'topic2',
                      group_id='my_consumer_group',
                      auto_commit_enable=True,
                      auto_commit_interval_ms=30 * 1000,
                      auto_offset_reset='smallest')

for m in kafka:
    process_message(m)
    kafka.task_done(m)
```
I believe it is related to this: https://issues.apache.org/jira/browse/KAFKA-993
The Apache Kafka docs say `API calls are not fully functional in releases until Kafka 0.8.1.1` here: https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol#AGuideToTheKafkaProtocol-OffsetCommit/FetchAPI