use fluent-langneg for subtag support

package.json

@@ -96,10 +96,10 @@
     "aws-sdk": "^2.149.0",
     "body-parser": "^1.18.2",
     "choo": "^6.5.1",
+    "cldr-core": "^32.0.0",
     "connect-busboy": "0.0.2",
     "convict": "^4.0.1",
     "express": "^4.16.2",
-    "express-request-language": "^1.1.15",
     "fluent": "^0.4.1",
     "fluent-langneg": "^0.1.0",
     "helmet": "^3.9.0",