[arch-devops] Archweb upgrade to django to 1.11

I've made a PR to update archweb to 1.11 the latest LTS version of django. [1] It's running on the staging env currently and no particular bugs have been found yet. Note that the staging env does not sync new packages, which I would love add soon (tm). [2] When this is merged, I'd like to deploy it as soon as possible on our production env. After this merge I want to focus on Python 3 / Django 2.0 although this is not a LTS release. (Python 3 alone should be enough work tbh). When would be a good time for an upgrade? Angvp / grazzolini please review the PR so it can be merged. [1] https://github.com/archlinux/archweb/pull/88 [2] https://archweb-dev.archlinux.org/ -- Jelle van der Waa