title: OnConfiguring has gone missing
body: <p>I'm attempting to update to EF7 beta5.  </p>
  
  <p>The compiler tells me that OnConfiguring is no longer a suitable method to override.  It also tells me that it can no longer find DbContextOptions or DbContextOptionsBuilder.</p>
  
  <p>Seems like i'm missing something here.  Can anyone enlighten me as to what this might be?</p>
  
  <pre><code>    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
      {
          string cnString = Config.Get("Data:" + _cnNm + ":ConnectionString");
  
          optionsBuilder.UseSqlServer(cnString);
  
      }
  </code></pre>