title: Display field choice as part of model string name
body: <p>From the <a href="https://docs.djangoproject.com/en/dev/ref/models/fields/#choices">django documentation</a>, what if I had</p>
  
  <pre><code>GENDER_CHOICES = (
      ('M', 'Male'),
      ('F', 'Female'),
  )
  
  class Person(models.Model):
      name = models.CharField(max_length=20)
      gender = models.CharField(max_length=1, choices=GENDER_CHOICES)
  
      def __str__(self):
              return "%s [%s]" % (self.name, self.gender)
  </code></pre>
  
  <p>What if I wanted the __str definition to display as the full name (Male or Female) for self.gender instead of M or F?</p>