Protowhat

- Support unicode when checking files
- Fix disabling parsing file content

- `Feedback` doesn't need to be subclassed in depending SCT libraries.
- `_debug` now has an `on_error` argument which can be set to `True` to show debugging info
on the next failure or before finishing.
- No NumPy dependency
- Simplified `State.report`

This release improves the base functionality for all depending SCT libraries.

- Add `_debug` SCT introspection function
- Add `State.parent_state` and `State.state_history` as a general state linking mechanism (using `State.creator`)
- Add `TestRunner` and `TestRunnerProxy` and make `Reporter` a `TestRunnerProxy`
- Add AST and text offset support in `Runner`
- Improve `Dispatcher`, `Feedback` and `Test` interfaces

This release enables protowhat to be the base for pythonwhat.

- `do_test` now runs a `Test` as in pythonwhat, instead of accepting a feedback string.
- the explicit Fail subclass should be used instead of relying on the old default implementation of `Test`
- the `report(feedback: Feedback)` method on the `State` class reintroduces a short way to gather exercise feedback,
equivalent to `do_test(Fail(Feedback(msg)))`, while also setting highlight info.
- the `legacy_signature` decorator enables to call a function using old argument names
when they are passed as keyword arguments
- AST utils to dump and load a tree structure to be used in e.g. dispatching are improved

- Update parsing class interface for compatibility with antlr-ast
- Support finding dynamic nodes in AST tree (instead of just custom defined nodes)
- Change `ckeck_edge` default value of `index` argument from `None` to `0`
- This is done to break less content
- Now: explicitly define the value of the `index` argument
- Later: revert default change and remove unnecessary explicit setting of the `index` argument

- Refactor based on refactor in `antlr-ast>=0.4.1`, `antlr-plsql>=0.7.0` and `antlr-tsql>=0.11.0`