[ANN] nFlow 7.1.0 released

[Edvard Fonsell]

Hello all,

nFlow 7.1.0 was released on March 25, 2020.

https://github.com/NitorCreations/nflow/releases/tag/7.1.0

**Highlights**
- `nflow-engine`
  - Add support for marking exceptions and workflow states as non-retryable. If processing the state method throws an exception, nFlow engine will check if it
    is allowed to retry. If not, the workflow instance will go directly to a failure/error state. See `NoRetryWorkflow` for example.

**Details**
- `nflow-engine`
  - Exceptions can be annotated with `@NonRetryable` to prevent retrying the state processing.
  - Add `isRetryable(Throwable thrown)` method to the `WorkflowState` interface with a default implementation that returns true when the thrown exception is not
    annotated with `@NonRetryable`.
  - Add default implementation for `WorkflowState.getDescription()` that returns the name of the state.