all: better API links in README

Change-Id: Iceca4836257d102335be2cd4e86fae8fb869f652
Reviewed-on: https://go-review.googlesource.com/37853
Run-TryBot: Quentin Smith <quentin@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

README.md

@@ -26,9 +26,9 @@ localperf -addr=:8080 -storage=localhost:8081
 ```
 
 The storage system is designed to have a
-[standardized API](storage/appengine/static/index.html), and we
+[standardized API](https://perfdata.golang.org/), and we
 encourage additional analysis tools to be written against the API. A
-client can be found in [storage/client](storage/client).
+client can be found in the [storage](https://godoc.org/golang.org/x/perf/storage) package.
 
 --