Interpreter states encapulated in an `Interpreter` instance.

Interpreter states encapulated in an `Interpreter` instance.

  - this was a big refactoring adds a few new files (chart.py, repl.py,
    config.py)

Fix: Errors stop on first failed handler.

Adding a new rule is safe. We check that the initializers run and there are no
aggregator conflicts before added the new rules to `Interpreter` state. We stage
propagation.

I've document a few more errors (see `examples/string-quote.dyna`)

Using the ~/.dyna directory

  - adds a dependency to the `path.py` module