Update reveal.js to version 3.7.0

There is a new reveal.js version out. As we try to keep up with
upstream, time to integreate it.

This patch updates reveal.js in for CDN-using instances as well as the
ones using the libraries.

Checked that speaker view in slide mode still works, so no CSP change
needed.

https://github.com/hakimel/reveal.js/releases/tag/3.7.0
2d241b9300/lib/csp.js (L72-L74)
Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>

package.json

@@ -110,7 +110,7 @@
     "raphael": "git+https://github.com/dmitrybaranovskiy/raphael",
     "readline-sync": "^1.4.7",
     "request": "^2.88.0",
-    "reveal.js": "~3.6.0",
+    "reveal.js": "~3.7.0",
     "scrypt": "^6.0.3",
     "select2": "^3.5.2-browserify",
     "sequelize": "^3.28.0",