Version 2.1.0 of statsample introduces the following changes:

• Update documentation to reflect methods that have been removed (@lokeshh)
• Update daru dependency to v0.1.6 (@lokeshh)
• Remove pre-daru legacy methods like n_valid, missing value functions (@lokeshh)
• Update test suite with rubocop and rake. New tests for methods like Regression (@lokeshh)
• Introduce fitting a regression using string formulas (@lokeshh)

This release updates dependencies and brings them at par with the latest releases of gems.

Specifically, spreadsheet and nmatrix gems have been updated.