Merge pull request #22 from matrix-org/federation_retries

synapse/federation/replication.py

synapse/federation/transport.py

synapse/handlers/federation.py

synapse/http/matrixfederationclient.py

synapse/rest/transactions.py

synapse/storage/__init__.py

synapse/storage/_base.py

synapse/storage/schema/delta/v9.sql

synapse/storage/schema/transactions.sql

synapse/storage/transactions.py

tests/federation/test_federation.py

tests/handlers/test_federation.py

tests/handlers/test_presence.py

tests/handlers/test_typing.py