Rename Item model to Task

- With matching model, view, template changes

todo/migrations/0006_rename_item_model.py

@@ -0,0 +1,19 @@
+# Generated by Django 2.0.3 on 2018-03-28 22:40
+
+from django.conf import settings
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('todo', '0005_auto_20180212_2325'),
+    ]
+
+    operations = [
+        migrations.RenameModel(
+            old_name='Item',
+            new_name='Task',
+        ),
+    ]