using force_text for indexing message.

verbose_name_plural may be a functional proxy object from ugettext_lazy,
it should be forced to be a string!
replacing `force_text` with `force_unicode`. #746
Merge pull request #746 from lazerscience/fix-update-index-output

Using force_text for indexing message
Make model filter for simple backend work

Adds Stefan Wehrmeyer to AUTHORS for patch
Merge pull request #761 from stefanw/simple-models-filter

Make models filter work on simple backend
Port the `from_python` method from pyelasticsearch to the Elasticsearch backend, similar to `to_python` in 181bbc2c010a135b536e4d1f7a1c5ae4c63e33db.

Fixes #762. Refs #759.