Custom LogoutView templates

I couldn't work out how to pass a custom ```template_name``` to the ```LogoutView```, like you can with other views (such as ```password_reset```). There may be a way to do this without editing the view itself (other creating another template named ```account/logout.html```), if there is I would be happy to know.

This branch lets you supply a ```template_name``` just like any of the other ```django-allauth``` views.
Tested on Python 2.7.4 and Django 1.5.1.

```python
from allauth.account import views as allauth_views

urlpatterns += patterns('',
    ....
    url(r"^logout/$", allauth_views.logout, {
        "template_name": "allauth/logout.html",
        }, name="account_logout"),
    ....
)
```