Adds back home/local/federated tabs

I don't think this is how I want the UI to work in the long run,
but for now it's better than not having it.
Fixes #210

bookwyrm/urls.py

@@ -45,6 +45,7 @@ urlpatterns = [
     re_path(r'^invite/(?P<code>[A-Za-z0-9]+)/?$', views.invite_page),
 
     path('', views.home),
+    re_path(r'^(?P<tab>home|local|federated)/?$', views.home_tab),
     re_path(r'^notifications/?', views.notifications_page),
     re_path(r'import/?$', views.import_page),
     re_path(r'import_status/(\d+)/?$', views.import_status),