title: Django Rest change primarykey in URL to use custom key
body: <p>i have two models Stats and Autor, how i can change primary key to use a unqiue field search by parameter(Subname in Autor model) i thinking about APIView but anyone can show me how use this?
  example : <a href="http://127.0.0.1:8000/autors/Subname" rel="nofollow noreferrer">http://127.0.0.1:8000/autors/Subname</a></p>
  
  <p>models.py</p>
  
  <pre><code>class Stats(models.Model):
  
  # Fields
  Word = models.CharField(name='Word',max_length=255)
  Word_count = models.IntegerField(name="Count")
  
  def __str__(self):
      return self.Word+":"+str(self.Count)
  
  class Autor(models.Model):
  
  name = models.CharField(max_length=255)
  sub_name = models.CharField(name='Subname', max_length=255, default='puste')
  # Relationship Fields
  words = models.ManyToManyField(Stats)
  </code></pre>
  
  <p>serializers.py</p>
  
  <pre><code>class StatsSerializer(serializers.ModelSerializer):
  class Meta:
      model=Stats
      fields=('Word','Count')
  
  class AutorSerializer(serializers.ModelSerializer):
  words=StatsSerializer(read_only=True,many=True)
  class Meta:
      model=Autor
      fields=('name','words')
  </code></pre>
  
  <p>Views.py</p>
  
  <pre><code>class AutorView(viewsets.ModelViewSet):
  queryset = Autor.objects.all()
  serializer_class = AutorSerializer
  
  class StatsView(viewsets.ModelViewSet):
      serializer_class = StatsSerializer
      queryset = Stats.objects.all()
  </code></pre>
  
  <p>Urls.py</p>
  
  <pre><code>from django.contrib import admin
  from django.urls import path,include
  from Teonite import views
  from rest_framework import routers
  
  router=routers.DefaultRouter()
  router.register('autors',views.AutorView)
  
  urlpatterns = [
      path('',include(router.urls))
  ]
  </code></pre>
  
  <p>I using django 2.0, python 3.6 and Django REST framework 3.8.2</p>