2015: add video link to "Stupid Gopher Tricks"

Change-Id: Ie6d2dd0a628082793cb53b6d65f38966df3ede5e
Reviewed-on: https://go-review.googlesource.com/14489
Reviewed-by: Andrew Gerrand <adg@golang.org>
diff --git a/2015/tricks.slide b/2015/tricks.slide
index f7fcfba..1746d77 100644
--- a/2015/tricks.slide
+++ b/2015/tricks.slide
@@ -5,6 +5,14 @@
 Andrew Gerrand
 adg@golang.org
 
+
+* Video
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+A video of this talk was recorded at GolangUK in London.
+
+.link https://www.youtube.com/watch?v=UECh7X07m6E Watch the talk on YouTube
+
+
 * This talk
 
 This talk is about things you might not know about Go.