Multiple city import not working

[ScottEAdams]

Checklist

• [X] I have verified that I am using a GIS-enabled database, such as PostGIS or Spatialite.
• [X] I have verified that that issue exists against the master branch of django-cities.
• [X] I have searched for similar issues in both open and closed tickets and cannot find a duplicate.

  182 - but I am leaving you the info you ask for :)

• [X] I have reduced the issue to the simplest possible case.
• [ ] I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

Steps to reproduce

As per the docs use filenames instead of filename and use an iterable (have tried all the obvious combinations.

CITIES_FILES = {
    'city': {
       'filenames': ["SE.zip", "FI.zip", "NO.zip"],
       'urls':      ['http://download.geonames.org/export/dump/'+'{filename}']
    },
}

python manage.py cities --import city

Expected behavior

Import!

Actual behavior

Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/project/lib/python3.5/site-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
    utility.execute()
  File "/project/lib/python3.5/site-packages/django/core/management/__init__.py", line 356, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/project/lib/python3.5/site-packages/django/core/management/base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/project/lib/python3.5/site-packages/django/core/management/base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "/Users/scott/.pyenv/versions/3.5.0/lib/python3.5/contextlib.py", line 30, in inner
    return func(*args, **kwds)
  File "/project/lib/python3.5/site-packages/cities/management/commands/cities.py", line 160, in handle
    func()
  File "/project/lib/python3.5/site-packages/cities/management/commands/cities.py", line 461, in import_city
    self.download('city')
  File "/project/lib/python3.5/site-packages/cities/management/commands/cities.py", line 177, in download
    filename = settings.files[filekey]['filename']
KeyError: 'filename'