Add flow duration curve module to metrics.

[jarq6c]

Adds a flow_duration_curve module to hydrotools.metrics. Includes methods for empirical FDCs, modeled FDCs (log pearson type iii), bootstrapping CIs, interpolation, conversion between exceedance probabilities and recurrence intervals, and flow variability indices.

Additions

• empirical_flow_duration_curve
• pearson_flow_duration_curve
• bootstrap_flow_duration_curve
• exceedance_values
• recurrence_values
• richards_flow_responsiveness

Removals

Changes

Testing

Notes

Todos

Checklist

• PR has an informative and human-readable title
• PR is well outlined and documented. See #12 for an example
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (see CONTRIBUTING.md)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output) using numpy docstring formatting
• Placeholder code is flagged / future todos are captured in comments
• Reviewers requested with the Reviewers tool ➡️

[GregoryPetrochenkov-NOAA]

This is good work! Everything is organized and well documented. My comments are merely nit picking but addressable at your discretion.

[jarq6c]

Thanks @GregoryPetrochenkov-NOAA I've implemented your recommendations.