title: AssertionError with custom user model django-allauth
body: <p>I'm new to django, recently i decide to integrate django allauth for using login with (facebook and google+), i work with a custom model (django 1.5), and a one to one userprofile model, my custom model class looks</p>
  
  <pre><code>class MyUser(AbstractBaseUser):   
     email = models.EmailField(
        verbose_name='email address',
        max_length=255,
        unique=True,
        db_index=True,
     )
     username = models.CharField(max_length=35,  blank=False)
     is_active = models.BooleanField (default=False)
     is_admin = models.BooleanField (default=False)
  
    objects = MyUserManager()
  
    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = ['username']
  </code></pre>
  
  <p>and my user profile :</p>
  
  <pre><code>class UserProfile(models.Model):
     phone = models.FloatField(blank=True, null=True)
     is_visible = models.BooleanField (default=True)
     user = models.OneToOneField(MyUser, primary_key=True)
  </code></pre>
  
  <p>here the django allauth local_settings file :</p>
  
  <pre><code>ACCOUNT_AUTHENTICATION_METHOD = "email"
  ACCOUNT_SIGNUP_FORM_CLASS = 'bloodi.accounts.forms.RegistrationForm'
  ACCOUNT_LOGOUT_ON_GET = True
  ACCOUNT_EMAIL_REQUIRED = True
  ACCOUNT_UNIQUE_EMAIL = True
  </code></pre>
  
  <p>with this configuration i met two problems with django allauth :<br>
     *) It doesn't allow a duplicate username 
     *) the application crash on sign up process  ( it seems like the user account must be active to continue to login)</p>
  
  <pre><code>AssertionError 
  Exception Location: \allauth\account\utils.py in perform_login, line 110
  ...
  assert user.is_active
  </code></pre>