Merge pull request #123 from matrix-org/postgres

docs/postgres.rst

scripts/port_from_sqlite_to_postgres.py

synapse/app/homeserver.py

synapse/config/database.py

synapse/handlers/_base.py

synapse/handlers/federation.py

synapse/handlers/login.py

synapse/handlers/message.py

synapse/handlers/room.py

synapse/notifier.py

synapse/push/pusherpool.py

synapse/storage/__init__.py

synapse/storage/_base.py

synapse/storage/appservice.py

synapse/storage/directory.py

synapse/storage/engines/__init__.py

synapse/storage/engines/postgres.py

synapse/storage/engines/sqlite3.py

synapse/storage/event_federation.py

synapse/storage/events.py