Remove image stuff from normal django_type cookiecutter.

This has niggled me in the past, but then the Pillow security upgrade made me think of it.

Can the following just be `{% if cookiecutter.django_type == 'cms' %}` I don't understand why the image stuff is included for normal django.

```
{% if cookiecutter.django_type == 'cms' or cookiecutter.django_type == 'normal' %}
easy-thumbnails==1.4
pillow==2.3.1
image_diet==0.7.1
{% endif %}
```
