title: EF 6 IsRequired() allowing empty strings
body: <p>In past projects with versions of EF5 and EF4, the IsRequired() fluent API method would thrown a DbEntityValidationException if the property was null or an empty string.  In my current project utilizng EF6, The DBEntityValidationException is not thrown when the string property is empty.</p>
  
  <p><strong>Entity:</strong></p>
  
  <pre><code>public class Application : BaseEntity
  {
      public string Name { get; set; }
  
      // navigation properties
      public IList&lt;Role&gt; Roles { get; set; }
  }
  </code></pre>
  
  <p><strong>Configuration:</strong></p>
  
  <pre><code>internal class ApplicationMapping : EntityTypeConfiguration&lt;Application&gt;
  {
      public ApplicationMapping()
      {
          // table name
          this.ToTable("Applications");
  
          // properties
          this.Property(t =&gt; t.Name)
              .IsRequired()
              .HasMaxLength(100);
      }
  }
  </code></pre>
  
  <p>After pouring over the MSDN EF documentation and stack overflow, I am at a loss for why this is happening.  Did a convention get added/modified to EF6?</p>