add ability to monitor admin action

stop execution of admin's actions if one or more records changed
Merge branch 'release/0.5' into develop
Merge branch 'feature/admin_actions' into develop
fixes python3 compatibility and removes deprecated
add install requirements to travis cfg
forced pk value of ConcurrentModel created in TestAdmin
forced pk value of ConcurrentModel created in TestAdmin

This was required to allow travis test to run.
Merge branch 'develop' of github.com:saxix/django-concurrency into develop
removes django-dynamic-fixtures due incompatibility python3
add ability to handle concurrency in admin with list_editable

see issue #10
Merge branch 'feature/list_editable' into develop
fixes travis build
removes dependency on actions for list_editable

related to #10
fixes add new record when list_editable enabled
fixes #12
adds ability to disable "sanity check" per single model

- new config management config.AppSettings
- new Manager.get_object_with_version
- new Model.get_concurrency_version
- add documetation
fixes travis tests
fixes postgres tests
add django 1.6a1 to travis
add disable_concurrency context manager