v0.1.0 - Initial Release

This marks the initial release of xsystem, which focuses on pub/sub and event-bus behavior.

• Adds an createEventBus behavior.
• Adds a withPubSub higher-order behavior.
• Adds a withHistory higher-order behavior.
• Adds subscribe and unsubscribe events.
• Adds a fromMachine helper to create a behavior.
• Adds a fromActor helper to create a service creator.

This package is still very muck work-in-progress and future releases are likely to contain breaking changes. The API is still experimental and might change with feedback and in response to new additions in XState.