doc: note the net/http CloseNotifier changes in go1.6.html

Also reference the new Transport.ExpectContinueTimeout after the
mention of 100-continue.

Fixes #13721

Change-Id: I3445c011ed20f29128092c801c7a4bb4dd2b8351
Reviewed-on: https://go-review.googlesource.com/18281Reviewed-by: Andrew Gerrand <adg@golang.org>

doc/go1.6.html

@@ -685,7 +685,8 @@ First, the
 <a href="/pkg/http/#FileServer"><code>FileServer</code></a> now sorts its generated directory listings by file name.
 Second, the
 <a href="/pkg/http/#Client"><code>Client</code></a> now allows user code to set the
-<code>Expect:</code> <code>100-continue</code> header.
+<code>Expect:</code> <code>100-continue</code> header (see
+<a href="/pkg/http/#Transport"><code>Transport.ExpectContinueTimeout</code></a>).
 Third, there are
 <a href="/pkg/net/http/#pkg-constants">four new error codes</a> from RFC 6585:
 <code>StatusPreconditionRequired</code> (428),
@@ -693,6 +694,14 @@ Third, there are
 <code>StatusRequestHeaderFieldsTooLarge</code> (431),
 and
 <code>StatusNetworkAuthenticationRequired</code> (511).
+Fourth, the implementation and documentation of
+<a href="/pkg/http/#CloseNotifier"><code>CloseNotifier</code></a>
+has been substantially changed.
+The <a href="/pkg/http/#Hijacker"><code>Hijacker</code></a>
+interface now works correctly on connections that have previously
+been used with <code>CloseNotifier</code>.
+The documentation now describes when <code>CloseNotifier</code>
+is expected to work.
 </li>
 
 <li>