title: Does elastalert work with ElasticSearch 6
body: <p>Have an elastalert docker image (<a href="https://hub.docker.com/r/ivankrizsan/elastalert/" rel="nofollow noreferrer">https://hub.docker.com/r/ivankrizsan/elastalert/</a>) that worked with elasticsearch 5.6, changed to a test environment with ElasticSearch 6.1 (no index)  and now get </p>
  
  <pre><code>Creating Elastalert index in Elasticsearch...
  Traceback (most recent call last):
    File "/usr/bin/elastalert-create-index", line 11, in &lt;module&gt;
      load_entry_point('elastalert', 'console_scripts', 'elastalert-create-index')()
    File "/opt/elastalert/elastalert/create_index.py", line 153, in main
      es.indices.put_mapping(index=index, doc_type='elastalert', body=es_mapping)
    File "build/bdist.linux-x86_64/egg/elasticsearch/client/utils.py", line 73, in _wrapped
    File "build/bdist.linux-x86_64/egg/elasticsearch/client/indices.py", line 282, in put_mapping
    File "build/bdist.linux-x86_64/egg/elasticsearch/transport.py", line 312, in perform_request
    File "build/bdist.linux-x86_64/egg/elasticsearch/connection/http_requests.py", line 90, in perform_request
    File "build/bdist.linux-x86_64/egg/elasticsearch/connection/base.py", line 125, in _raise_error
  elasticsearch.exceptions.RequestError: TransportError(400, u'mapper_parsing_exception', u'No handler for type [string] declared on field [aggregate_id]')
  </code></pre>