Added a setting where the exported excel files should be stored.

Added a option to send the exported excel as mail attachment.

src/mahjong_ranking/views.py

@@ -7,7 +7,7 @@ from django.contrib import auth
 from django.contrib.auth.mixins import LoginRequiredMixin, \
     PermissionRequiredMixin
 from django.contrib.messages.views import SuccessMessageMixin
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.utils.translation import ugettext as _
 from django.views import generic