title: "Add New" to foreign key field in django modelform
body: <p>I'm pretty new to this, apologies if i'm unclear....</p>
  
  <p>running django, with bootstrap, and i've been fiddling with django-bootstrap. BootstrapModelForm is pretty cool, i didn't include the django-bootstrap stuff in my example, but i though i should note.</p>
  
  <p>I have models:</p>
  
  <pre><code>class spam(models.Model):
     name = models.CharField()
  
  class Eggs(models.Model):
     spam = models.ForiegnKey('spam')
  </code></pre>
  
  <p>I use a modelform,something like:</p>
  
  <pre><code>class EggsForm(forms.ModelForm):
     meta:
        model=Eggs
  </code></pre>
  
  <p>EggsForm allows selection of which spam will be referenced by eggs.
  I noticed the admin interface has a cool way to either select or add another egg. </p>
  
  <p>How can i get similar functionality into my create form?</p>