Set moment default timezone to UTC

This requires switching to the moment-timezone package.
This is for consistensy with knexfile, which already sets the DB timezone to UTC.

package-lock.json

@@ -27,6 +27,14 @@
         "@types/node": "*"
       }
     },
+    "@types/moment-timezone": {
+      "version": "0.5.6",
+      "resolved": "https://registry.npmjs.org/@types/moment-timezone/-/moment-timezone-0.5.6.tgz",
+      "integrity": "sha512-rMZjLmXs9sly1UbwxckyAEvQkrwrGqR24nFAjFrndRJBBnUooCCD0LPmdRcf9haHXFnckI9E3ko0oC6LEDk7dw==",
+      "requires": {
+        "moment": ">=2.14.0"
+      }
+    },
     "@types/node": {
       "version": "8.10.20",
       "resolved": "https://registry.npmjs.org/@types/node/-/node-8.10.20.tgz",
@@ -2629,6 +2637,14 @@
       "resolved": "https://registry.npmjs.org/moment/-/moment-2.22.2.tgz",
       "integrity": "sha1-PCV/mDn8DpP/UxSWMiOeuQeD/2Y="
     },
+    "moment-timezone": {
+      "version": "0.5.21",
+      "resolved": "https://registry.npmjs.org/moment-timezone/-/moment-timezone-0.5.21.tgz",
+      "integrity": "sha512-j96bAh4otsgj3lKydm3K7kdtA3iKf2m6MY2iSYCzCm5a1zmHo1g+aK3068dDEeocLZQIS9kU8bsdQHLqEvgW0A==",
+      "requires": {
+        "moment": ">= 2.9.0"
+      }
+    },
     "ms": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/ms/-/ms-2.0.0.tgz",