Django-elasticsearch-metrics

Changes:

* *Backwards-incompatible*: Change default template pattern to
`<appname>_<metricname>_<date>`.

Bug fixes:

* Pin to elasticsearch-dsl>=6.0.0,<6.3.0 because version 6.3.0
introduces an incompatiblity.

Bug fixes:

* Fix `check_metrics` exiting with an error when "number_of_shards" or
"number_of_replicas" is set on a metric.

Bug fixes:

* Don't set `_all` on mappings. This prevents a DeprecationWarning in
Elasticsearch 6.

Bug fixes:

* Fix inheritance of `Index` settings.

Features:

* Add `Metric.check_index_template`, which checks that the state of the
metric is in sync with the index template in Elasticsearch.
* *Backwards-incompatible*: Remove `Metric.check_index_template_exists`.
Use `Metric.check_index_template` instead.

Bug fixes:

* Fix bug where different `Metric` subclasses were sharing the same
index settings (incl. mappings).

Other changes:

* *Backwards-incompatible*: Rename `Metric.create_index_template` to
`Metric.sync_index_template`.