Update kafka0.10

[johnmpage]

Hi Taylor,

The submitted changes provide the following:

1. Updated to work with Kafka 0.10. (And will likely work with any version after 0.8, but this has not been tested)
2. Provides a simple properties "pass-through" mechanism, so that all 49 Kafka Producer properties can be leveraged. This also means the appender will require less maintenance as these properties evolve in Kafka 0.11+ as long as the core Producer initialization remains constant.
3. Added an option to log to System out while setting up.
4. Added an option to log method and line number in the JSONFormatter.

There is another decent appender out there by D. Wegener, but this appender's property "pass-through" strategy is simpler and more powerful, imho.

Thanks, John Page

Note: Yes, we used to work together. You may recall, we went to an ETE together. I hope you're doing well!