Add `{error, Reason}` to typespecs
Add `{error, Reason}` to typespecs

`fabric:design_docs/1` and `all_docs/5` can return `{error, Reason}`

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