Signing activities

I hope it works correctly…

Fixes #6

migrations/2018-05-03-182555_blogs_add_keys/down.sql

@@ -0,0 +1,3 @@
+-- This file should undo anything in `up.sql`
+ALTER TABLE blogs DROP COLUMN private_key;
+ALTER TABLE blogs DROP COLUMN public_key;

migrations/2018-05-03-182555_blogs_add_keys/up.sql

@@ -0,0 +1,3 @@
+-- Your SQL goes here
+ALTER TABLE blogs ADD COLUMN private_key TEXT;
+ALTER TABLE blogs ADD COLUMN public_key TEXT NOT NULL DEFAULT '';