Notify kafka restart on config changes

should resolve issue #42
alternative is to solve via wrapper cookbook:

```
[
  ::File.join(node[:kafka][:config_dir], node[:kafka][:log4j_config]),
  ::File.join(node[:kafka][:config_dir], node[:kafka][:config]),
  kafka_init_opts[:env_path],
  kafka_init_opts[:script_path]
].each do |template|

  begin
    r = resources(template: template)
    r.notifies(:restart, "service[kafka]")
  rescue Chef::Exceptions::ResourceNotFound
    log "Kafka template file not found: '#{template}' -- skipping restart notification"
  end

end
```