upgrade Google.Apis.Auth dependency to 0.15.0
diff --git a/src/csharp/Grpc.Auth/project.json b/src/csharp/Grpc.Auth/project.json
index 6a1c9fc..ffa4e7c 100644
--- a/src/csharp/Grpc.Auth/project.json
+++ b/src/csharp/Grpc.Auth/project.json
@@ -23,13 +23,13 @@
   },
   "dependencies": {
     "Grpc.Core": "1.0.0-pre2",
-    "Google.Apis.Auth": "1.11.1"
+    "Google.Apis.Auth": "1.15.0"
   },
   "frameworks": {
     "net45": { },
     "netstandard1.5": {
       "imports": [
-        "net45"
+        "portable-net45"
       ],
       "dependencies": {
         "Microsoft.NETCore.Portable.Compatibility": "1.0.1",
diff --git a/templates/src/csharp/Grpc.Auth/project.json.template b/templates/src/csharp/Grpc.Auth/project.json.template
index b3244e4..19d4b42 100644
--- a/templates/src/csharp/Grpc.Auth/project.json.template
+++ b/templates/src/csharp/Grpc.Auth/project.json.template
@@ -25,13 +25,13 @@
     },
     "dependencies": {
       "Grpc.Core": "${settings.csharp_version}",
-      "Google.Apis.Auth": "1.11.1"
+      "Google.Apis.Auth": "1.15.0"
     },
     "frameworks": {
       "net45": { },
       "netstandard1.5": {
         "imports": [
-          "net45"
+          "portable-net45"
         ],
         "dependencies": {
           "Microsoft.NETCore.Portable.Compatibility": "1.0.1",