Fix nuget GAC issues

src/Discord.Net/project.json

@@ -1,5 +1,5 @@
 {
-  "version": "0.9.0-rc3",
+  "version": "0.9.0-rc3-2",
   "description": "An unofficial .Net API wrapper for the Discord client.",
   "authors": [
     "RogueException"
@@ -63,8 +63,14 @@
     },
     "net45": {
       "frameworkAssemblies": {
-        "System.Runtime": "4.0.0.0",
-        "System.Threading.Tasks": "4.0.0.0"
+        "System.Runtime": {
+          "type": "build",
+          "version": ""
+        },
+        "System.Threading.Tasks": {
+          "type": "build",
+          "version": ""
+        }
       },
       "dependencies": {
         "WebSocket4Net": "0.14.1",