Merges in changes from our ES7 branch, and drops support for ES5.
This is a breaking change due to the upgrade, we have a ES5 branch at the commit before this.
These tests verify that, given an index settings and mappings, data can be written to the index, and read from it with a query_all query. These are very simple sanity tests.
We can, and should, write more complex tests that specific to each index in the future.
