Fix Django 1.10 deprecation of MIDDLEWARE_CLASSES

[dolan-a]

MIDDLEWARE_CLASSES is deprecated in Django 1.10 and instead MIDDLEWARE will replace it at some point.

[aaugustin]

This was fixed in 388e177 a month ago, unless you have something else in mind?

I think it's best to wait until all versions < 1.10 are no longer supported to change the documentation.

[dolan-a]

I'm running toolbar v1.5, and I'm getting a warning from manage.py runserver:

?: (1_10.W001) The MIDDLEWARE_CLASSES setting is deprecated in Django 1.10 and the MIDDLEWARE setting takes precedence. Since you've set MIDDLEWARE, the value of MIDDLEWARE_CLASSES is ignored.

If I remove debug_toolbar from installed apps, the warning goes away. Here's the django code that triggers the warning. After grepping the toolbar code, I don't see what is triggering the error. Thoughts?

[aaugustin]

Ah that's because you're using the implicit setup. Use the explicit setup instead, as recommended in the documentation.

[dolan-a]

Ah great, that should fix it, although it looks like I'll have to wait till #864 gets merged into a release (currently getting the already-fixed error described in #869)