Release 2.2.0
- Don't use Nokogumbo directly, as it's included in Nokogiri >= 1.12.
- Move string unescaping from LL1::Lexter to new Unescape module.
- Implement :unescape option to PEG terminals.
- Allow start_production for PEG to specify case insensitive_strings, mapping to either :upper or :lower. Transforms the matched string component of a production to either upper or lower case.