(#136) - Skip test PUT attachment with invalid _rev

When running this against Cloudant it appears to fail intermittently.
Cloudant will occasionally return an invalid / truncated response -
looks to be a bug on the Cloudant end which we're looking into.
(#136) - Cloudant fixes for test.changes.js

Generally, do not rely on integer / predictable update sequences.
(#136) - Skip testing against _view filters in _changes.

Cloudant does not support using view functions as filters.
(#136) - Skip test for last_seq in _changes

The order of _changes is non-deterministic in clustered CouchDB
(BigCouch / Cloudant) so this test is invalid.