Changelog:
- Renamed all nodes by removing their 'AST` prefix and 'Node' suffix;
- The usage of `repr()` and `str()` for nodes has been swapped. `repr()` gives a debug view while `str()` gives the yield;
- Tree structure changes:
- `Text` is no longer inherited from, instead it is a regular node inheriting from the abstract class `Leaf` that takes it place;
- `Comment` is not a leaf node, it uses `Literal` and `Text` nodes for it content and other `Comment` nodes for recursion;
- `Repetition` does not hold the count in a variable anymore, instead it uses the new `Number` node that is a `Leaf`.
- `AST` has been renamed to `PT`;
- New errors are defined for usage in this package instead of `SyntaxError`. With the new errors comes the ability to handle parsing errors in the form of partial parse trees. See the documentation for details.
- Tests cover more parts of a node's structure.