Merge branch 'feature/list-streaming' into 'develop'

MastoAPI: Add streaming for lists.

See merge request pleroma/pleroma!183

priv/repo/migrations/20180530123448_add_list_follow_index.exs

@@ -0,0 +1,7 @@
+defmodule Pleroma.Repo.Migrations.AddListFollowIndex do
+  use Ecto.Migration
+
+  def change do
+    create index(:lists, [:following])
+  end
+end