fix vimeo engine and add comments

engine generate (Error: None), I don't know why

searx/settings.yml

@@ -153,11 +153,7 @@ engines:
 
   - name : vimeo
     engine : vimeo
-    categories : videos
-    results_xpath : //div[@id="browse_content"]/ol/li
-    url_xpath : ./a/@href
-    title_xpath : ./a/div[@class="data"]/p[@class="title"]/text()
-    content_xpath : ./a/img/@src
+    locale : en-US
     shortcut : vm
 
 locales: