Modernize admin template overrides - admin.site.site_header being ignored in Django 1.7

[ghost]

When using django 1.7 the admin.site.site_header = field is being ignored so your site still shows Django Admin at the top. Is this easily fixed?

[bufke]

I would guess this would involve updating the templates in massadmin/templates/admin to be more modern (or better yet override as little as possible). It certainly seems fixable. I can't commit the time though for a minor cosmetic issue. I'd be happy to accept a pull request.