title: Getting __init__() got an unexpected keyword argument 'instance' with CreateView of Django
body: <h1>Some details:</h1>
  <pre><code>Request Method: GET
  Request URL: http://localhost:8080/user/create
  Django Version: 1.5.1
  Exception Type: TypeError
  Exception Value: ____init____() got an unexpected keyword argument 'instance'
  Exception Location: /place/venv/local/lib/python2.7/site-packages/django/views/generic/edit.py in get_form, line 35
  Python Executable: /place/venv/bin/python
  Python Version: 2.7.3
  </code></pre>
  <h1>views.py</h1>
  <pre><code>class UserCreateView(CreateView):
      model = models.User
      form_class = forms.UserForm
  </code></pre>
  <h1>urls.py</h1>
  <pre><code>url(r'^user/create$', UserCreateView.as_view(), name='user_create'),
  </code></pre>
  <h1>forms.py</h1>
  <pre><code>class UserForm(forms.Form):
      GROUP_CHOICES = [(-1, '[Choose]')]
      GROUP_CHOICES += [(group.id, group.name.capitalize()) for group in auth.models.Group.objects.all()]
  
      email = forms.EmailField(
          label='Email',
          widget=forms.TextInput(attrs={'placeholder': 'Email'})
      )
      first_name = forms.CharField(
          label='First Name',
          widget=forms.TextInput(attrs={'placeholder': 'First Name'})
      )
      last_name = forms.CharField(
          label='Last Name',
          widget=forms.TextInput(attrs={'placeholder': 'Last Name'})
      )
      password = forms.CharField(
          label='Password',
          widget=forms.PasswordInput(attrs={'placeholder': 'Password'})
      )
      password_validation = forms.CharField(
          label='Repeat Password',
          widget=forms.PasswordInput(attrs={'placeholder': 'Repeat Password'})
      )
      mobile_number = forms.CharField(
          label='Mobile Number',
          widget=forms.TextInput(attrs={'placeholder': 'Mobile Number'})
      )
      office_number = forms.CharField(
          label='Office Number',
          widget=forms.TextInput(attrs={'placeholder': 'Office Number'})
      )
      group = forms.ChoiceField(
          label='Group',
          choices=GROUP_CHOICES
      )
  
      def clean_password_validation(self):
          if self.cleaned_data['password'] == self.cleaned_data['password_validation']:
              return self.cleaned_data['password_validation']
          else:
              raise forms.ValidationError('Passwords don\'t match')
  
      def clean_group(self):
          if self.cleaned_data['group'] != -1:
              return self.cleaned_data['group']
          else:
              raise forms.ValidationError('Please, choose a group')
  </code></pre>
  <h1>models.py</h1>
  <pre><code>class User(models.Model):
      user = models.OneToOneField(auth.models.User)
      mobile_number = models.CharField(max_length=64)
      office_number = models.CharField(max_length=64)
  </code></pre>