v0.4.0

Flatten model weights instead of using lists.
Fix minor issues, update documentation.

• PB-116: pin docutils version (#259) [Corentin Henry]
• PB-119 update isort config and calls (#260) [janpetschexain]
• PB-351 Store participant metrics (#244) [Robert Steiner]
• Adjust isort config (#258) [Robert Steiner]
• PB-366 flatten weights (#253) [janpetschexain]
• PB-379 Update black setup (#255) [Anastasiia Tymoshchuk]
• PB-387 simplify serve module (#251) [Corentin Henry]
• PB-104: make the tests fast again (#252) [Corentin Henry]
• PB-122: handle sigint properly (#250) [Corentin Henry]
• PB-383 write aggregated weights after each round (#246) [Corentin Henry]
• PB-104: Fix exception in monitor_hearbeats() (#248) [Corentin Henry]
• DO-57 Update docker-compose files for provisioning InfluxDB (#249) [Ricardo Saffi Marques]
• DO-59 Provision Redis 5.x for persisting states for the Coordinator (#247) [Ricardo Saffi Marques]
• PB-381: make the log level configurable (#243) [Corentin Henry]
• PB-382: cleanup storage (#245) [Corentin Henry]
• PB-380: split get_logger() (#242) [Corentin Henry]
• XP-332: grpc resource exhausted (#238) [Robert Steiner]
• XP-456: fix coordinator command (#241) [Corentin Henry]
• XP-485 Document revised state machine (#240) [kwok]
• XP-456: replace CLI argument with a config file (#221) [Corentin Henry]
• DO-48 ❄️ 🚀 Build stable package on git tag with SemVer (#234) [Daniel Kravetz]
• XP-407 update documentation (#239) [janpetschexain]
• XP-406 remove numpy file cli (#237) [janpetschexain]
• XP-544 fix aggregate module (#235) [janpetschexain]
• DO-58: cache xain-fl dependencies in Docker (#232) [Corentin Henry]
• XP-479 Start training rounds from 0 (#226) [kwok]