Parsion

Lot of updates, API starting to stabilize.

Added:
- Type hinting and better types
- Refactor of parser, to keep lexer and parser independent
- Improved error handling and error handler API

Improved documentation, with examples.

- Significant refactoring of main class
- 100% pytest-cov test coverage
- Cleanup and fix formatting

Changes:
- Updated API to take grammar as class constants
- Added error handling
- Improved compilation speed

It is working and up for testing.

It can:
- Generate parsers
- Parse strings
- Give some Exceptions for usage

What it doesn't have
- Error recovery
- Really useful error messages
- A stable API (even though I don't expect it to get big changes)

Feel free to open issues for feedback