add schema version to docs

lib/processor.js

@@ -5,7 +5,7 @@ const URL = require('url');
 
 class Processor {
   constructor() {
-    }
+  }
 
   process(request) {
     let handler = this[request.type];
@@ -15,7 +15,9 @@ class Processor {
       return request.document;
     }
 
-    return handler.call(this, request);
+    const result = handler.call(this, request);
+    result._metadata.version = 1;
+    return result;
   }
 
   collection(request) {