doc: clean up docs page, refer to wiki, change install doc paths

R=golang-dev, minux.ma, r
CC=golang-dev
https://golang.org/cl/5728051
diff --git a/doc/install-source.html b/doc/install-source.html
index 21cda8a..5a17844 100644
--- a/doc/install-source.html
+++ b/doc/install-source.html
@@ -1,6 +1,6 @@
 <!--{
 	"Title": "Installing Go from source",
-	"Path": "/install/source/"
+	"Path": "/doc/install/source"
 }-->
 
 <h2 id="introduction">Introduction</h2>
@@ -15,7 +15,7 @@
 <p>
 Most users don't need to do this, and will instead install
 from precompiled binary packages as described in
-<a href="/doc/install.html">Getting Started</a>,
+<a href="/doc/install">Getting Started</a>,
 a much simpler process.
 If you want to help develop what goes into those precompiled
 packages, though, read on.
@@ -29,7 +29,7 @@
 compiler and tools (<code>6g</code>, <code>8g</code> etc.).
 For information on how to work on <code>gccgo</code>, a more traditional
 compiler using the GCC back end, see
-<a href="/doc/gccgo_install.html">Setting up and using gccgo</a>.
+<a href="/doc/install/gccgo">Setting up and using gccgo</a>.
 </p>
 
 <p>