doc: move wiki tutorial into articles directory, rmdir doc/codelab

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5701050

doc/codelab/wiki/index.html → doc/articles/wiki/index.html

-<!-- Codelab: Writing Web Applications -->
+<!--{
+	"Title": "Writing Web Applications"
+}-->
+
 <h2>Introduction</h2>
 
 <p>
-Covered in this codelab:
+Covered in this tutorial:
 </p>
 <ul>
 <li>Creating a data structure with load and save methods</li>
@@ -33,7 +36,7 @@ Install Go (see the <a href="/doc/install.html">Installation Instructions</a>).
 </p>
 
 <p>
-Make a new directory for this codelab and cd to it:
+Make a new directory for this tutorial and cd to it:
 </p>
 
 <pre>

doc/codelab/wiki/wiki.html → doc/articles/wiki/wiki.html

-<!-- Codelab: Writing Web Applications -->
+<!--{
+	"Title": "Writing Web Applications"
+}-->
+
 <h2>Introduction</h2>
 
 <p>
-Covered in this codelab:
+Covered in this tutorial:
 </p>
 <ul>
 <li>Creating a data structure with load and save methods</li>
@@ -33,7 +36,7 @@ Install Go (see the <a href="/doc/install.html">Installation Instructions</a>).
 </p>
 
 <p>
-Make a new directory for this codelab and cd to it:
+Make a new directory for this tutorial and cd to it:
 </p>
 
 <pre>

doc/docs.html

@@ -65,7 +65,7 @@ Answers to common questions about Go.
 <h3>Other introductory articles</h3>
 
 <ul>
-<li><a href="codelab/wiki/">Writing Web Applications</a> - 
+<li><a href="/doc/articles/wiki/">Writing Web Applications</a> - 
 	building a simple web application.</li>
 <li><a href="go_for_cpp_programmers.html">Go for C++ Programmers</a></li>
 </ul>

doc/install-source.html

@@ -235,8 +235,8 @@ read <a href="/doc/code.html">How to Write Go Code</a>.
 </p>
 
 <p>
-Build a web application by following the <a href="/doc/codelab/wiki/">Wiki
-Codelab</a>.
+Build a web application by following the <a href="/doc/articles/wiki/">Wiki
+Tutorial</a>.
 </p>
 
 <p>

doc/install.html

@@ -153,8 +153,8 @@ read <a href="/doc/code.html">How to Write Go Code</a>.
 </p>
 
 <p>
-Build a web application by following the <a href="/doc/codelab/wiki/">Wiki
-Codelab</a>.
+Build a web application by following the <a href="/doc/articles/wiki/">Wiki
+Tutorial</a>.
 </p>
 
 <p>