Update Json.NET to 9.0.1-beta1

src/Microsoft.Extensions.Configuration.Json/project.json

@@ -22,7 +22,7 @@
   "dependencies": {
     "Microsoft.Extensions.Configuration": "1.0.0-*",
     "Microsoft.Extensions.Configuration.FileExtensions": "1.0.0-*",
-    "Newtonsoft.Json": "8.0.3"
+    "Newtonsoft.Json": "9.0.1-beta1"
   },
   "frameworks": {
     "net451": {