Track Subject Location and Metadata Changes

Closes #47
Test if resource_name is defined first
Correctly create polymorphic link for versioned item
Only test api links if they've been defined
Merge pull request #213 from edpaget/subject-versions

Track Subject Location and Metadata Changes
Install Sidekiq
Add Kafka gems
Start working on kafka adapter class
Finish abstract kafka producer implementation
Add JBundler to manage kafka jar deps
Remove crap from application.rb
Add KafkaEvent concern
Add ClassificationWorker to handle background processing
Update Classifications Controller Specs
Add Kafka publishing from classification lifecycle
Add specs for multi kafka producer
Add kafka and sidekiq intializers
Update Vagrantfile and Dockerfile to use jbundle when in jruby
Add example config for sidekiq and kafka
Fix to load Poseidon under MRI