Support older setuptools
Support older setuptools

It turns out that older setuptools requires that there be commas
in dependency specifiers while newer versions are a bit more relaxed.

Since older versions need to at least parse the specifiers in order
to upgrade themselves, we need to use the older format if we want
to support the older versions _at all_, even if we aren't targetting
them.

Obviously having made this change we don't actually need a newer
version of setuptools, so we don't add a specific dependency there.

Previously this would error with:

```
Collecting django-cache-toolbox==0.3.1
  Downloading https://files.pythonhosted.org/packages/eb/f7/f39a121ade50b873b8dbd9f285c3c02810d08e96404e1ca2d6546b48db86/django-cache-toolbox-0.3.1.tar.gz
    Complete output from command python setup.py egg_info:
    error in django-cache-toolbox setup command: 'install_requires' must be a string or list of strings containing valid project/version requirement specifiers

    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-install-187om0y_/django-cache-toolbox/
```

lamby/django-cache-toolbox