Added sample data and better examples

Improvements

• Added sample data based on test data
• Cleaned up code comments
• Added examples to methods

Breaking Changes

• Renamed aki() to aki_staging() for more consistent method names

Bug fixes

• Fixed bug when n < m for combn() in combn_changes()
• Changed methods from method.default() to method.data.frame() to prevent infinite recursion on incorrectly specified function arguments

Documentation available at https://alwinw.github.io/epocakir/