Send 'nosniff' header (fixes #97)

Change-Id: If9670a66a9402da77616a362ceda8ea47aceaa75
diff --git a/t/page.t b/t/page.t
index 4339f4e..68e2c25 100644
--- a/t/page.t
+++ b/t/page.t
@@ -31,6 +31,7 @@
   ->header_like('Content-Security-Policy', qr!nonce-!)
   ->content_like(qr/<script nonce/)
   ->content_like(qr/document\.body\.classList\.remove\(\'no-js\'\);/)
+  ->header_is('X-Content-Type-Options', 'nosniff')
   ;
 
 # Test additions