Fix performance issue with form fields.

The form_field.choices was evaluated, causing SQL queries for each `ModelChoiceField`.

(backported from 2.1a1; a8d896c7788b29260994619692b930c27d81d7ab)
Updated AUTHORS for django-any-urlfield

Thanks @borgstrom, @kingel, @jjanssen, @vitaly4uk for your contributions!
Bump version to 2.0.1
Merge branch 'v2.0.x'

Conflicts:
	CHANGES.rst
	any_urlfield/__init__.py
	docs/conf.py