Use minimal packages

Author: nbarbettini

src/Stormpath.AspNetCore/project.json

@@ -22,9 +22,6 @@
   "description": "Stormpath middleware for ASP.NET Core. Easily adds authentication and authorization to ASP.NET Core applications.",
   "frameworks": {
     "netstandard1.6": {
-      "dependencies": {
-        "NETStandard.Library": "1.6.0"
-      },
       "imports": "dotnet"
     }
   },