Merge in pull requests, compatibility fixes for librdkafka v0.9.0.99 and kafka v0.9.0.1

[jsermeno]

Hi,

I merged in a few pending pull requests, added fixes, and updated examples to work with librdkafka v0.9.0.99, and kafka v0.9.0.1. Here's an overview of the changes:

• Merge in Support for High-Level consumer and librdkafka >0.9 (master) #19.
• Merge in fixed consumeMessageBatch to report properly EOF #15.
• Include an executable example that accepts options. This makes it easier to customize, and debug any issues.
• Added section on how to run examples in README.md.
• Fix segfaults caused by calling fetchBrokerMetadata and related methods. Updating c2hs to v0.28.1 fixes this problem. See Segmentation fault in fetchBrokerMetadata #20.
• Fix hanging processes when using consumers due to not calling rd_kafka_message_destroy soon enough.
• All tests pass. This is due to the above changes, and I also removed the check for consuming keyed messages, since the partition depends on the key. I haven't seen an easy way to consume messages based on key, perhaps the high-level consumer api can do this?

Thanks again for the library, I really like the API.