requirementsascode v0.2.1

Pre-release of requirementsascode, with the following features:

• Document a use case model, actors, use cases, use case flows, use case steps, events
• Run the use case model for a particular actor
• Specify cross-cutting concerns, e.g. measuring performance.

Limitations include:

• No support for included use cases or subflows so far

What's new:

• Support for cross-cutting concerrn (new constructor parameter for UseCaseRunner)
• New example project for cross-cutting concerns
• Added unit tests for hello world examples
• Reworked helloworld examples to reflect new, testable version