Django 1.10 compatibility

The module does not work on Django 1.10, because use of patterns is [deprecated since Django 1.8](https://docs.djangoproject.com/en/1.9/ref/urls/#patterns):

```python
  File "/.../python2.7/site-packages/genericadmin/admin.py", line 5, in <module>
    from django.conf.urls import patterns, url
ImportError: cannot import name patterns
```