countdown: fields for sending reminders

extending countdown items in order to have them also store reminders,
which are the same idea (an event at a time) but these are watched by
the irc bot and sent to the specified destination when the time is
reached

this adds support for configuring this, code in support of it is coming
in later commits

bss/dr.botzo#11

countdown/migrations/0003_auto_20170222_2025.py

@@ -0,0 +1,35 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.5 on 2017-02-23 02:25
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('countdown', '0002_remove_countdownitem_source'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='countdownitem',
+            name='is_reminder',
+            field=models.BooleanField(default=False),
+        ),
+        migrations.AddField(
+            model_name='countdownitem',
+            name='reminder_message',
+            field=models.TextField(default=''),
+        ),
+        migrations.AddField(
+            model_name='countdownitem',
+            name='reminder_target',
+            field=models.CharField(default='', max_length=64),
+        ),
+        migrations.AddField(
+            model_name='countdownitem',
+            name='sent_reminder',
+            field=models.BooleanField(default=False),
+        ),
+    ]