Merge branch 'release-v0.5.1' of github.com:matrix-org/synapse

CHANGES.rst

README.rst

UPGRADE.rst

VERSION

scripts/check_signature.py

setup.py

synapse/__init__.py

synapse/api/auth.py

synapse/api/errors.py

synapse/api/events/__init__.py

synapse/api/events/validator.py

synapse/app/homeserver.py

synapse/app/synctl.py

synapse/crypto/event_signing.py

synapse/crypto/keyclient.py

synapse/crypto/keyring.py

synapse/federation/replication.py

synapse/federation/units.py

synapse/handlers/_base.py

synapse/handlers/directory.py