Initial release of parser combinator library for Python:
- Fundamental parsers: literal, alternative, sequential
- Common parsers: optional, discard left and right, regex
- Repeated parsers: rep, rep1, repsep, rep1sep
- Forward declarations inside context
- Standard sequence context `GeneralParsers`
- Whitespace ignoring context `TextParsers`
- Examples: expression, JSON
- Complete unit test suite
- Basic tutorial