[release-branch.go1.4] doc: scrub references to code.google.com

These are the references that affect current Go users.
I left intact references in older release notes;
we can figure out what to do with them later.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/186140043

Conflicts:
	doc/go1.4.html

Change-Id: I1032686f2b3ac6dacaf8f114b8c35cdf221330ca
diff --git a/doc/contrib.html b/doc/contrib.html
index 8a674d6..93a609f 100644
--- a/doc/contrib.html
+++ b/doc/contrib.html
@@ -50,7 +50,7 @@
 
 <h2 id="resources">Developer Resources</h2>
 
-<h3 id="source"><a href="https://code.google.com/p/go/source">Source Code</a></h3>
+<h3 id="source"><a href="https://golang.org/change">Source Code</a></h3>
 <p>Check out the Go source code.</p>
 
 <h3 id="golang-dev"><a href="https://groups.google.com/group/golang-dev">Developer</a> and
@@ -76,13 +76,13 @@
 
 <h2 id="howto">How you can help</h2>
 
-<h3><a href="https://code.google.com/p/go/issues">Reporting issues</a></h3>
+<h3><a href="//golang.org/issue">Reporting issues</a></h3>
 
 <p>
 If you spot bugs, mistakes, or inconsistencies in the Go project's code or
 documentation, please let us know by
-<a href="https://code.google.com/p/go/issues/entry">filing a ticket</a>
-on our <a href="https://code.google.com/p/go/issues">issue tracker</a>.
+<a href="//golang.org/issue/new">filing a ticket</a>
+on our <a href="//golang.org/issue">issue tracker</a>.
 (Of course, you should check it's not an existing issue before creating
 a new one.)
 </p>
@@ -101,8 +101,8 @@
 guidelines</a> for information on design, testing, and our code review process.
 </p>
 <p>
-Check <a href="https://code.google.com/p/go/issues">the tracker</a> for 
+Check <a href="//golang.org/issue">the tracker</a> for 
 open issues that interest you. Those labeled
-<a href="https://code.google.com/p/go/issues/list?q=status=HelpWanted">HelpWanted</a>
+<a href="https://github.com/golang/go/issues?q=is%3Aopen+is%3Aissue+label%3Ahelpwanted">helpwanted</a>
 are particularly in need of outside help.
 </p>