remove categories which has been replaces by taxonomies in utils

opentech/categories/migrations/0001_initial.py

-# -*- coding: utf-8 -*-
-# Generated by Django 1.10 on 2016-10-31 10:47
-from __future__ import unicode_literals
-
-from django.db import migrations, models
-
-
-class Migration(migrations.Migration):
-
-    initial = True
-
-    dependencies = [
-    ]
-
-    operations = [
-        migrations.CreateModel(
-            name='Category',
-            fields=[
-                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
-                ('name', models.CharField(max_length=128)),
-            ],
-            options={
-                'verbose_name_plural': 'categories',
-                'verbose_name': 'category',
-            },
-        ),
-    ]

opentech/categories/models.py

-from django.db import models
-
-from wagtail.wagtailsnippets.models import register_snippet
-from wagtail.wagtailadmin.edit_handlers import FieldPanel
-
-
-@register_snippet
-class Category(models.Model):
-    name = models.CharField(max_length=128)
-
-    panels = [
-        FieldPanel('name', classname="full"),
-    ]
-
-    class Meta:
-        verbose_name = 'category'
-        verbose_name_plural = 'categories'
-
-    def __str__(self):
-        return self.name