go.talks: Fixing typo and wrong comment on code

R=adg, r.eklind.87, bradfitz
diff --git a/2014/go4java.slide b/2014/go4java.slide
index 3025c62..57def5f 100644
--- a/2014/go4java.slide
+++ b/2014/go4java.slide
@@ -259,7 +259,7 @@
 The method receiver is a copy of a pointer (pointing to the same address).
-Method calls on nil receivers are perfectly valid (and useulf!).
+Method calls on nil receivers are perfectly valid (and useful!).
 	func (p *Person) Name() string {
 		if p == nil {
diff --git a/2014/go4java/writecounter.go b/2014/go4java/writecounter.go
index 9fc9647..fd5a247 100644
--- a/2014/go4java/writecounter.go
+++ b/2014/go4java/writecounter.go
@@ -12,7 +12,7 @@
 	_ = os.Stdout
-// WriteCounter counts how many times `Write` is called
+// WriteCounter tracks the total number of bytes written.
 type WriteCounter struct {
 	count int