add teamsnap preferences page.

teamsnap/models.py

@@ -1 +1,9 @@
 # Create your models here.
+from django.db import models
+
+from benchcoach.users.models import User
+
+
+class Preferences(models.Model):
+    user = models.OneToOneField(User, on_delete=models.CASCADE)
+    managed_team_id = models.IntegerField()