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
```

I couldn't set the expectation on the instantiated consumer object because these methods are in the constructor.  So just instantiating it would case these methods to get run before I could stub them.  This way, I can set the expectation on any instance that *will* be instantiated.