Minor change to ReactNative.csproj path. (#14)

Author: rozele

templates/windows.js

@@ -305,7 +305,7 @@ packages/
     <EmbeddedResource Include="Properties\${name}.rd.xml" />
   </ItemGroup>
   <ItemGroup>
-    <ProjectReference Include="..\..\node_modules\react-native-windows\ReactWindows\ReactNative\ReactNative.csproj">
+    <ProjectReference Include="$(ReactWindowsRoot)\react-native-windows\ReactWindows\ReactNative\ReactNative.csproj">
       <Project>{c7673ad5-e3aa-468c-a5fd-fa38154e205c}</Project>
       <Name>ReactNative</Name>
     </ProjectReference>