plugin/health: doc updates (#1582)

Fixes #1564

plugin/health/README.md

@@ -6,7 +6,9 @@
 
 ## Description
 
-By enabling *health* any plugin that implements it will be queried for it's health. The combined
+By enabling *health* any plugin that implements
+[healt.Healther interface](https://godoc.org/github.com/coredns/coredns/plugin/health#Healther)
+will be queried for it's health. The combined
 health is exported, by default, on port 8080/health .
 
 ## Syntax
@@ -42,7 +44,7 @@ If monitoring is enabled (via the *prometheus* directive) then the following met
 
 * `coredns_health_request_duration_seconds{}` - duration to process a /health query. As this should
   be a local operation it should be fast. A (large) increases in this duration indicates the
-  CoreDNS process is having trouble keeping up.
+  CoreDNS process is having trouble keeping up with its query load.
 
 ## Examples
 

plugin/health/healther.go

 package health
 
-// Healther interface needs to be implemented by each plugin willing to
-// provide healthhceck information to the health plugin. As a second step
-// the plugin needs to registered against the health plugin, by addding
-// it to healthers map. Note this method should return quickly, i.e. just
-// checking a boolean status, as it is called every second from the health
-// plugin.
+// Healther interface needs to be implemented by each plugin willing to provide
+// healthhceck information to the health plugin. Note this method should return
+// quickly, i.e. just checking a boolean status, as it is called every second
+// from the health plugin.
 type Healther interface {
 	// Health returns a boolean indicating the health status of a plugin.
 	// False indicates unhealthy.