Fixed incompatibility with CouchDB's _changes feed
Fixed incompatibility with CouchDB's _changes feed

CouchDB also supports POST to _changes but expects most of the parameters
to still be in the URL, not the request body.

Fixes #1139

amco/couchbase-lite-ios,amco/couchbase-lite-ios,couchbase/couchbase-lite-ios,amco/couchbase-lite-ios,brendand/couchbase-lite-ios,amco/couchbase-lite-ios,brendand/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,couchbase/couchbase-lite-ios,amco/couchbase-lite-ios,amco/couchbase-lite-ios,brendand/couchbase-lite-ios,brendand/couchbase-lite-ios,couchbase/couchbase-lite-ios,amco/couchbase-lite-ios,couchbase/couchbase-lite-ios,brendand/couchbase-lite-ios