ticket:10 add Log model
ticket:10 add south migration
ticket:10 register Log on admin page
ticket:10 add additional fields

Added 'model' and 'instance' fields
ticket:10 add unit test for logging
ticket:10 factory_boy .create() didn't save data

Force call save()
ticket:10 fix syntax

fails on QuerySet[-1] so reverse order by 'order_by'
ticket:10 PEP8 tests format
ticket:10 Fix typo in tests (deleted wrong record)
ticket:10 add realization
ticket:10 fix hooks to avoid duplicate lines

test case for some reason calls hooks twice