Use custom user model in tests
Merge branch 'master' into test-with-custom-user-model

Conflicts:
	wagtail/tests/models.py
	wagtail/tests/utils.py
	wagtail/wagtailcore/tests/test_page_permissions.py
	wagtail/wagtaildocs/tests.py
Merge branch 'test-with-custom-user-model' of https://github.com/kaedroho/wagtail into kaedroho-test-with-custom-user-model

Conflicts:
	runtests.py
	wagtail/tests/utils.py
remove newly-added references to User in test_account_management
Merge branch 'kaedroho-test-with-custom-user-model'