Added flake8 config to tox.ini.
Merge pull request #278 from wrwrwr/feature/flake8-config

Include flake8 config in tox.ini.
Let's check if flake8 in travis can read parameters from tox.ini.
Set TabbedTranslationAdmin class depending on Django version. Added a new class for Django 1.5 which depends on older jquery/jquery-ui versions. Updated the jquery/jquery-ui versions for the existing admin classes (ref #270).
Update deprecated imports with Django >= 1.7
Merge pull request #283 from amarandon/master

Update deprecated imports with Django >= 1.7
Made sync_translation_fields command respect the verbosity option.
Refactored sync_translation_fields for better readability.
Made it possible to run sync/update_translation_fields limited to models
from a single app.

There is a new command line option "--app" for both commands that takes
an app label. You can also directly pass an AppConfig or a pre-1.7 app
(models module) as a call_command argument, which is handy when executing
the commands as part of a post_migrate/syncdb handler.
Coded a test for sync_translation_field.

The DirtyRegistryTestBase restores the registry after each test, unlike
TestAutodiscover that did it only after the whole test case was finished.
This is needed for test_update_command if it happens to run after
sync_update_command, but should also make autodiscovery tests more robust.
Demangled sync/update_translation_fields from modeltranslation settings.

This lets you register one field with a set of AVAILABLE_LANGUAGES and
DEFAULT_LANGUAGE, register another one with different settings, and still
have the commands work properly.

Mostly useful for mixing modeltranslation tests with project tests --
project may use a different set of languages than those enforced by the
test settings.
Taught reload_app to clean up translator registry from dangling models.
Refactored the main test base to avoid some module reloading.

Reloading the translator module is better avoided at all as it creates a
copy of the registry, making debugging tests harder. A lighter option
could be resetting the registry, but because we're preventing registration
of test models before enforcing test settings this is not necessary.

Reloading modeltranslation settings was leaving references to pre-existing
settings in other modules and that could cause some surprises.

Note that there is still some reloading and some globals black magic.
It would be nice to to get rid of it completely, but we'd need to provide
unpatching of models (such that unregistering would be equivalent to not
registering).
Shortened a couple of translator.translator phrases.
Removed the test_settings.py file and moved the statement to tests.py for
simplicity.

If there is some use for a separate file I'm not aware of this should be
simple to revert.
Limited test_update_command to the modeltranslation.tests models.

This prevents its failure trying to update user-models registered
with languages different than the test languages.
Made test_registration only count models from modeltranslation.tests app.

The only thing that was preventing the test from failing in the context
of a project with its own models registered for translation was the
translator registry duplication, which was removed in 1e566f4e.

The models count change is due to no longer considering the single
registered model from "managed_app".