Change SteamKit2 filesystem project reference to NuGet package reference

DepotDownloader.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio 14
+# Visual Studio 15
-VisualStudioVersion = 14.0.23107.0
+VisualStudioVersion = 15.0.26228.4
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DepotDownloader", "DepotDownloader\DepotDownloader.csproj", "{39159C47-ACD3-449F-96CA-4F30C8ED147A}"
 EndProject

DepotDownloader/DepotDownloader.csproj

@@ -5,11 +5,9 @@
     <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
     <RuntimeIdentifiers>win7-x86;win7-x64;ubuntu.16.10-x64;osx.10.12-x64</RuntimeIdentifiers>
   </PropertyGroup>
-  <ItemGroup>
-    <ProjectReference Include="..\..\SteamKit\SteamKit2\SteamKit2\SteamKit2.csproj" />
-  </ItemGroup>
   <ItemGroup>
     <PackageReference Include="protobuf-net" Version="2.1.0" />
+    <PackageReference Include="SteamKit2" Version="2.0.0-Alpha" />
     <PackageReference Include="system.componentmodel.typeconverter" Version="4.3.0" />
   </ItemGroup>
 </Project>