Some basic test support
Fixing tests for different Django versions

Formset management fields output generation changed depending on Django
version.
Making sure variable is present

This avoids InvalidVarException checking, which enforces safe way of
using template variables.
Exploit from_iterable for Contexts with no __dict__

As @nvie pointed out to me, my earlier patch "breaks for people who are using Jingo/Jinja2 templates, since their Context has no attribute __dict__."

So after a couple of suggestions, we realized, and I've tested this locally too, that this new approach works well (for probably all applicable cases).
Updating CHANGELOG and CONTRIBUTORS
Bumping version to 1.2.8