replace old option_list with parser.add_argument

[aesmail]

This brings the ./manage.py push_ios_notification command up to date with django 1.8+

[aesmail]

I guess this will drop support for django <= 1.7

[stephenmuss]

Seems fine to me. I'm ok with it if you can update the travis config to include Django 1.10 and remove Django 1.6 and 1.7.

[joshowen]

Hopefully this will be merged in soon https://github.com/svetlyak40wt/django-fields/pull/50 to fix the 1.10 issues.