Remove the django>=1.4.2 dependency in setup.py

[synw]

Would it be possible to remove the django>=1.4.2 dependency from setup.py?

Reason: now that Django 2 is out it makes me download it which is not what I want. It is annoying for a module I have that depends on django-pandas.

[chrisdev]

@synw looks like we'll be removing support for all versions of Django before 1.8