A few documentation fixes

The misspelling of `import` is ultimately harmless, although it does look a tad careless.

The incorrect citation of Django 1.3+'s [KEY_PREFIX](https://docs.djangoproject.com/en/1.3/ref/settings/#key-prefix) (which remains [unchanged](https://docs.djangoproject.com/en/1.6/ref/settings/#key-prefix) in 1.6) is super, super dangerous.

I've not verified the instructions for sub-1.3 versions, and since 1.4 is now the oldest supported version of Django anyway, it's probably not a particularly good idea to endorse using such old versions.