Update reveal.js to 3.7.0

Change-Id: Id15b52df33897447221283166a4a1d1249a38774
Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
(cherry picked from commit 7e6262c1acb6556611c05c63ddd61421cf57ec35)

diff --git a/docs/com/pres/reveal.js b/docs/com/pres/reveal.js
index a349ff4..2c5396b 160000 (submodule)
--- a/docs/com/pres/reveal.js
+++ b/docs/com/pres/reveal.js
@@ -1 +1 @@
-Subproject commit a349ff43c58c23f9c837b8ea9b5fc7d4761b8de3
+Subproject commit 2c5396b7d347f8ee1344016f15b93d4f78401569