Fixed #120 -- Explicitly sotre tax values

src/pretix/base/migrations/0006_auto_20160211_1630.py

@@ -0,0 +1,27 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9 on 2016-02-11 16:30
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0005_auto_20160211_1459'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='orderposition',
+            name='tax_rate',
+            field=models.DecimalField(decimal_places=2, default=0, max_digits=7, verbose_name='Tax rate'),
+            preserve_default=False,
+        ),
+        migrations.AddField(
+            model_name='orderposition',
+            name='tax_value',
+            field=models.DecimalField(decimal_places=2, default=0, max_digits=10, verbose_name='Tax value'),
+            preserve_default=False,
+        ),
+    ]