x/text: minor documentation fixes

Correct repo name in README.md. Correct binary name in gotext
documentation.

Change-Id: I9541fe023e52be8332d0500934fbe77c353d6cb6
Reviewed-on: https://go-review.googlesource.com/122469
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>

README.md

diff --git a/README.md b/README.md
index b3f365e..c6d2c25 100644
--- a/README.md
+++ b/README.md
@@ -89,5 +89,5 @@
 this repository, see https://golang.org/doc/contribute.html.
 
 The main issue tracker for the image repository is located at
-https://github.com/golang/go/issues. Prefix your issue with "x/image:" in the
+https://github.com/golang/go/issues. Prefix your issue with "x/text:" in the
 subject line, so it is easy to find.

cmd/gotext/doc.go

diff --git a/cmd/gotext/doc.go b/cmd/gotext/doc.go
index 2a274f7..0e19297 100644
--- a/cmd/gotext/doc.go
+++ b/cmd/gotext/doc.go
@@ -24,7 +24,7 @@
 //
 // Usage:
 //
-// 	go extract <package>*
+// 	gotext extract <package>*
 //
 //
 //
@@ -33,7 +33,7 @@
 //
 // Usage:
 //
-// 	go rewrite <package>
+// 	gotext rewrite <package>
 //
 // rewrite is typically done once for a project. It rewrites all usages of
 // fmt to use x/text's message package whenever a message.Printer is in scope.
@@ -45,7 +45,7 @@
 //
 // Usage:
 //
-// 	go generate <package>
+// 	gotext generate <package>
 //
 //
 //