title: System.Reactive/Rx .NET 4.0 on Nuget
body: <p>I am trying to add <code>System.Reactive.Core</code> to a .NET 4.0 project using VS2013 and getting the following error:</p>
  
  <pre><code>Could not install package `System.Reactive.Core 3.0.0`. 
  You are trying to install this package into a project that target 
  `.NETFramework,Version=v4.0`, but the package does not contain any assembly 
  reference or content files that are compatible with that framework.
  </code></pre>
  
  <p>I also cannot find the old Rx-Main packages anymore on <code>nuget.org</code>.</p>
  
  <p>How can I get Rx Installed on .NET 4.0?</p>
  
  <p>I guess I will have to manually go find the RxMain 2.x libs and reference them directly from a lib folder in my solution?</p>