ref(pkg/chartutil): improve comment for PathValue

Make comment for PathValue more explanatory.

pkg/chartutil/values.go

@@ -388,7 +388,13 @@ func istable(v interface{}) bool {
 	return ok
 }
 
-// PathValue takes a yaml path with . notation and returns the value if exists
+// PathValue takes a path that traverses a YAML structure and returns the value at the end of that path.
+// The path starts at the root of the YAML structure and is comprised of YAML keys separated by periods.
+// Given the following YAML data the value at path "chapter.one.title" is "Loomings".
+//
+// 		chapter:
+//		  one:
+//		    title: "Loomings"
 func (v Values) PathValue(ypath string) (interface{}, error) {
 	if len(ypath) == 0 {
 		return nil, errors.New("YAML path string cannot be zero length")