Add Microsoft.NETCore.Platforms to the projects that have to be built with dnu

src/Microsoft.Dnx.Watcher.Core/project.json

@@ -14,7 +14,8 @@
       "version": "1.0.0-*"
     },
     "Microsoft.Extensions.Logging.Abstractions": "1.0.0-*",
-    "Microsoft.Extensions.FileSystemGlobbing": "1.0.0-*"
+    "Microsoft.Extensions.FileSystemGlobbing": "1.0.0-*",
+    "Microsoft.NETCore.Platforms": "1.0.1-*"
   },
   "frameworks": {
     "dnx451": {

src/Microsoft.Dnx.Watcher/project.json

@@ -9,7 +9,8 @@
         "Microsoft.Dnx.Watcher.Core": "1.0.0-*",
         "Microsoft.Extensions.CommandLineUtils": "1.0.0-*",
         "Microsoft.Extensions.Logging": "1.0.0-*",
-        "Microsoft.Extensions.Logging.Console": "1.0.0-*"
+        "Microsoft.Extensions.Logging.Console": "1.0.0-*",
+        "Microsoft.NETCore.Platforms": "1.0.1-*"
     }, 
     "frameworks": {
         "dnx451": { },

test/Microsoft.Dnx.Watcher.Tests/project.json

@@ -6,6 +6,7 @@
     "dependencies": {
         "Microsoft.Extensions.PlatformAbstractions": "1.0.0-*",
         "Microsoft.Dnx.Watcher": "1.0.0-*",
+        "Microsoft.NETCore.Platforms": "1.0.1-*",
         "xunit.runner.aspnet": "2.0.0-aspnet-*"
     },
     "frameworks": {