v0.2.0-rc4

• Fixed Added Postgres compatibility.
• Fixed manual bridging (!tg bridge) for unauthenticated users.
• Fixed inviting unauthenticated Matrix users from Telegram (via /invite <mxid>).
• Changed Alembic to read database path from the config, so editing alembic.ini is no longer necessary. Use alembic -x config=/path/to/config.yaml ... to specify the config path.