Reference fix

Author: gedem

src/NetCoreStack.WebSockets/project.json

@@ -5,7 +5,8 @@
     "NETStandard.Library": "1.6.1",
     "Microsoft.AspNetCore.WebSockets": "1.0.0",
     "Microsoft.Extensions.Logging": "1.1.0",
-    "Newtonsoft.Json": "9.0.1"
+    "Newtonsoft.Json": "9.0.1",
+    "System.IO.Compression": "4.3.0"
   },
 
   "frameworks": {