Switching to generations TFMs

src/Microsoft.AspNet.Antiforgery/project.json

@@ -13,9 +13,8 @@
     "Microsoft.Extensions.OptionsModel": "1.0.0-*",
     "Microsoft.Extensions.WebEncoders": "1.0.0-*"
   },
-
-  "frameworks" : {
-    "dnx451": { },
-    "dnxcore50" : { }
+  "frameworks": {
+    "net451": {},
+    "dotnet5.4": {}
   }
 }