Better name for method running checks

This also avoids name clash with Model method in Django 1.7.

Signed-off-by: Michal Čihař <michal@cihar.com>
Fix typo in test name

Signed-off-by: Michal Čihař <michal@cihar.com>
Specify Django version ranges rather than being explict

Signed-off-by: Michal Čihař <michal@cihar.com>