title: <class> has no foreign key to <class> in Django when trying to inline models
body: <p>I need to be able to create a quiz type application with 20 some odd multiple choice questions. </p>
  
  <p>I have 3 models: <code>Quizzes</code>, <code>Questions</code>, and <code>Answers</code>. </p>
  
  <p>I want in the admin interface to create a quiz, and inline the quiz and answer elements.</p>
  
  <p>The goal is to click "Add Quiz", and be transferred to a page with 20 question fields, with 4 answer fields per each in place. </p>
  
  <p>Here's what I have currently:</p>
  
  <pre><code>class Quiz(models.Model):
      label = models.CharField(blank=true, max_length=50)
  
  class Question(models.Model):
      label = models.CharField(blank=true, max_length=50)
      quiz = models.ForeignKey(Quiz)
  
  class Answer(models.Model):
      label = models.CharField(blank=true, max_length=50)
      question = models.ForeignKey(Question)
  
  class QuestionInline(admin.TabularInline):
      model = Question
      extra = 20
  
  class QuestionAdmin(admin.ModelAdmin):
      inlines = [QuestionInline]
  
  class AnswerInline(admin.TabularInline):
      model = Answer
      extra = 4
  
  class AnswerAdmin(admin.ModelAdmin):
      inlines = [AnswerInline]
  
  class QuizAdmin(admin.ModelAdmin):
      inlines = [QuestionInline, AnswerInline]
  
  admin.site.register(Question, QuestionAdmin)
  admin.site.register(Answer, AnswerAdmin)
  admin.site.register(Quiz, QuizAdmin)
  </code></pre>
  
  <p>I get the following error when I try to add a quiz:</p>
  
  <pre><code>class 'quizzer.quiz.models.Answer'&gt; has no ForeignKey to &lt;class 'quizzer.quiz.models.Quiz'&gt;
  </code></pre>
  
  <p>Is this doable, or am I trying to pull too much out of the Django Admin app? </p>