增加了组内可见的公告，编辑了对应的 models 和 js

announcement/migrations/0002_auto_20150818_1445.py

@@ -0,0 +1,26 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('group', '0004_merge'),
+        ('announcement', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='announcement',
+            name='groups',
+            field=models.ManyToManyField(to='group.Group'),
+        ),
+        migrations.AddField(
+            model_name='announcement',
+            name='is_global',
+            field=models.BooleanField(default=True),
+            preserve_default=False,
+        ),
+    ]