Revert "use couch_db calls instead of couch_btree"
Revert "use couch_db calls instead of couch_btree"

We can't do this without other changes since couch_db:get_design_docs
is hard coded to skip deleted documents, and that's incompatible with
how _changes is supposed to behave.

This reverts commit e41d226dca11dc8b24d6c011cc3014e6c553db42.

fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb