doc: update installing and usage instructions

Change-Id: Idbbcdc2359805c5cbe090d804c81550930d760f2
Reviewed-on: https://go-review.googlesource.com/19456
Reviewed-by: Andrew Gerrand <adg@golang.org>

README

diff --git a/README b/README
index 9113cbc..b9c4d63 100644
--- a/README
+++ b/README
@@ -3,17 +3,17 @@
 
 All benchmarks are compiled into a single binary, to build it execute:
 
-	go install golang.org/x/benchmarks/bench
+	go get golang.org/x/benchmarks/bench
 
 When you run the binary without any flags, it prints comma-separated list of
 available benchmarks:
 
-	./bench
+	bench
 	build,garbage,http,json
 
 To run a benchmark execute:
 
-	./bench -bench=json
+	bench -bench=json
 
 The binary has a number of flags to control benchmark duration, etc.
 Run 'bench -help' to get the full list of flags.