(#136) - Fix "Testing all docs" against clustered CouchDB

In Cloudant / CouchDB 2.0, the _changes feed is composed from
multiple shards and there is no guarantee that ordering
will be consistent between multiple calls.

The fix is just to test that the changes feed includes the entries
we require regardless of the order.
(#136) - Fix "Testing deleting in changes" against clustered CouchDB

Given that we cannot assume the order of a changes feed on Cloudant /
CouchDB 2.0, test that the change is included in the _changes feed
following the initial database sequence number.
(#136) - Fix "Testing include docs" against clustered CouchDB

The ordering of the changes feed is non-deterministic so just test that
the expected entry is present.
(#136) - Fix "Testing conflicts" in _changes against clustered CouchDB

_changes is unordered in a clustered CouchDB so remove this assumption
from the test.