Merge pull request django-haystack#1313 from chrisbrooke/Fix-elasticsearch-2.0-meta-data-changes

ElasticSearch: remove deprecated boost mapping section

Thanks to @chrisbrooke for the patch

Author: acdha

haystack/backends/elasticsearch_backend.py

@@ -135,10 +135,6 @@ def setup(self):
         current_mapping = {
             'modelresult': {
                 'properties': field_mapping,
-                '_boost': {
-                    'name': 'boost',
-                    'null_value': 1.0
-                }
             }
         }