feature_request(metrics): support all Radon metrics

[Kristinita]

1. Summary

It would be nice if Xenon will support all Radon code metrics.

2. Example of expected behavior

A user run the command:

xenon kira_example_file.py {#args}

Where {#args} are Xenon command-line arguments for all metrics.

Xenon will compute:

1. Cyclomatic Complexity (as radon cc)
2. Maintainability Index (as radon mi)
3. Raw Metrics (as radon raw)
4. Halstead Complexity Metrics (as radon hal)

3. Justification of the need of the feature

Users may want to use all Radon metrics in Continuous Integration. Currently, Xenon compute solely the Cyclomatic Complexity, and Radon doesn’t support non-zero exit codes unlike Xenon.

Thanks.