Upgrade Ocsigen Toolkit version

Author: balat

opam

@@ -18,7 +18,7 @@ depends: [
   "safepass" {>= "3.0"}
   "ocsigen-i18n" {>= "3.1.0"}
   "eliom" {>= "6.10.1"}
-  "ocsigen-toolkit" {>= "2.3.1"}
+  "ocsigen-toolkit" {>= "2.7.0"}
   "yojson" {>= "1.4.1"}
   "resource-pooling" {>= "1.0" & < "2.0"}
   "cohttp-lwt-unix"