removing superuser required from slow queries, and added documentation

Author: merencia

README.md

@@ -2,13 +2,21 @@
 
 A Prometheus exporter for some postgresql metrics.
 
+## Getting Started
+
 You can add as many database connections as you like to the
 `config.yml` file, and run it with:
 
 ```console
 ./postgresql_exporter -config=my/config.yml
 ```
 
+Some stats are hidden from normal database users, so you must grant acess to that:
+
+```sql
+GRANT pg_monitor to my_monitor_user;
+```
+
 Then you can add hostname:9111 to the prometheus scrapes config:
 
 ```yml
@@ -25,4 +33,4 @@ graph and alert on them.
 
 ```console
 docker run -p 9111 -v /path/to/my/config.yml:/config.yml caninjas/postgresql_exporter
-```
+```

gauges/slow_queries.go

@@ -28,10 +28,6 @@ func (g *Gauges) SlowestQueries() *prometheus.GaugeVec {
 		},
 		[]string{"query"},
 	)
-	if !g.isSuperuser {
-		log.Warn("postgresql_slowest_queries disabled because it requires a superuser to see queries from other users")
-		return gauge
-	}
 	if !g.hasExtension("pg_stat_statements") {
 		log.Warn("postgresql_slowest_queries disabled because pg_stat_statements extension is not installed")
 		return gauge