Simple java consumer

Creates a simple blocking java consumer.  It is expected that this code is executed inside of a thread (or something similar)


```ruby
# $bundle exec jruby hermann_test.rb


require 'hermann'
require 'hermann/provider/java_simple_consumer'
require 'hermann_jars'

zookeeper = "localhost:2181"
groupId   = "group1"
topic     = 'test'

example = Hermann::Provider::JavaSimpleConsumer.new(zookeeper, groupId, topic)

example.get_messages do |msg|
  puts "Recv: #{msg}"
end
```

This is a pretty big constructor which I'm not terribly fond of, I think some of these are optional that should have sane defaults, and some are required.

Here's which I think is which, correct me if you disagree:

**Required**:
 * topic
 * groupid
 * zookeepers

**Optional**:
* everything else :P

The 'required list' above is all I think we need from the user of `Hermann::Consumer` to construct a sane consumer object, the others we should choose sane defaults IMO and let them be overwritten if the user chooses