fix db.name for backwards compat

Author: nolanlawson

lib/index.js

@@ -34,7 +34,10 @@ exports.plugin.dump = utils.toPromise(function (writableStream, opts, callback)
 
   var PouchDB = self.constructor;
 
-  var output = new PouchDB(self.name, {
+  // db.name replaced db._db_name in pouch 6.0.0
+  /* istanbul ignore next */
+  var dbName = self.name || self._db_name;
+  var output = new PouchDB(dbName, {
     adapter: 'writableStream'
   });
   output.setupStream(writableStream);