修改group的models添加小组管理员的多对多字段，把原来的管理员字段重命名为创建者

group/migrations/0006_auto_20151209_1834.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9 on 2015-12-09 10:34
+from __future__ import unicode_literals
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('group', '0005_joingrouprequest_accepted'),
+    ]
+
+    operations = [
+        migrations.RenameField(
+            model_name='group',
+            old_name='admin',
+            new_name='created_by',
+        ),
+    ]

group/migrations/0007_auto_20151209_1836.py

@@ -0,0 +1,38 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9 on 2015-12-09 10:36
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('group', '0006_auto_20151209_1834'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='AdminGroupRelation',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('group', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='group.Group')),
+                ('user', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL)),
+            ],
+            options={
+                'db_table': 'admin_group_relation',
+            },
+        ),
+        migrations.AddField(
+            model_name='group',
+            name='admin',
+            field=models.ManyToManyField(related_name='managed_groups', through='group.AdminGroupRelation', to=settings.AUTH_USER_MODEL),
+        ),
+        migrations.AlterUniqueTogether(
+            name='admingrouprelation',
+            unique_together=set([('user', 'group')]),
+        ),
+    ]