Overall summary of changes:

• Update copyright (much more easier to use)
• Improved naming throughout the library
• Improved error handling
• Improved interface for handling arguments and options
• Rename the library: now officially Cling!
• Switch to array system for Cling::Parser (much better now)
• Improved interpreting for Cling::Executor
• Support for multiple values for options
• Support all-positional arguments
• Improved Cling::Value interface including exceptions
• Support Cling::Value extensions and add some default ones
• Improved interface for formatter
• (library) Improved specs and coverage
• (library) Improved documentation and examples