Merge pull request #319 from prometheus/recommend-grafana

Recommend Grafana over PromDash.

content/docs/visualization/grafana.md

 ---
 title: Grafana
-sort_rank: 7
+sort_rank: 2
 ---
 
 # Grafana support for Prometheus

content/docs/visualization/promdash.md

 ---
 title: PromDash
-sort_rank: 2
+sort_rank: 7
+toc: full-width
 ---
 
 # PromDash
 
+CAUTION: <b>NOTE:</b> We recommend [Grafana](/docs/visualization/grafana) for
+visualization of Prometheus metrics nowadays, as it has native Prometheus
+support and is widely adopted and powerful. There will be less focus on
+PromDash development in the future.
+
 ## Overview
 
 PromDash is a browser-based dashboard builder for Prometheus. It is a