doc: add qualified mention of dep to FAQ

This adds a qualified mention of golang/dep to the FAQ.

Fixes #19049

Change-Id: I42a114a008a6ca1250d849872dd98fd6523fa659
Reviewed-on: https://go-review.googlesource.com/46005Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/go_faq.html

@@ -1140,7 +1140,7 @@ program is one tool to help automate this process.
 </p>
 
 <p>
-The Go 1.5 release includes an experimental facility to the
+The Go 1.5 release added a facility to the
 <a href="https://golang.org/cmd/go">go</a> command
 that makes it easier to manage external dependencies by "vendoring"
 them into a special directory near the package that depends upon them.
@@ -1148,6 +1148,13 @@ See the <a href="https://golang.org/s/go15vendor">design
 document</a> for details.
 </p>
 
+<p>
+Work is underway on an experimental package management tool,
+<a href="https://github.com/golang/dep"><code>dep</code></a>, to learn
+more about how tooling can help package management. More information can be found in
+<a href="https://github.com/golang/dep/blob/master/FAQ.md">the <code>dep</code> FAQ</a>.
+</p>
+
 <h2 id="Pointers">Pointers and Allocation</h2>
 
 <h3 id="pass_by_value">