go.talks: corrections to "What's in a name?"

LGTM=dan.kortschak
R=golang-codereviews, dan.kortschak
CC=golang-codereviews
https://golang.org/cl/154370044
diff --git a/2014/names.slide b/2014/names.slide
index 328db80..199a7fa 100644
--- a/2014/names.slide
+++ b/2014/names.slide
@@ -78,10 +78,10 @@
 	func RuneCount(b []byte) int {
 		i, n := 0, 0
 		for i < len(b) {
-			if p[i] < RuneSelf {
+			if b[i] < RuneSelf {
 				i++
 			} else {
-				_, size := DecodeRune(p[i:])
+				_, size := DecodeRune(b[i:])
 				i += size
 			}
 			n++