title: The type or namespace IAppBuilder could not be found(missing using a directive pr an assembly reference)
body: <p>I am working on an Asp.Net MVC 4 Application in which I am using SignalR 2.0.1 and I Mapped it using Owin Startup class and it worked fine at first.</p>
  
  <p>All of a sudden when I tried to rebuild my app it said that the type are namespace <code>IAppbuilder</code> could not be found.</p>
  
  <p>Following is my start up class</p>
  
  <pre><code>using Microsoft.Owin;
  using Owin;
  using WhiteBoardApp;
  
  namespace WhiteBoardApp
  {
      public class Startup
      {
          public void Configuration(IAppBuilder app)
          {
              app.MapSignalR();
          }
      }
  }
  </code></pre>
  
  <p>I have installed <code>Owin</code> package too, and for some reasons I could not find Owin Startup class so I just added a normal class and included all the references that are needed. 
  May I know where I am making a mistake</p>