Bespokelang

- Fixed bug where `Undefined function` would not show the function which was undefined
- Improved auto-flushing of output buffer

- Program is now assumed to be in UTF-8

- Fixed behavior of `DO ROTINVERSE` with an argument outside the range from 1 to the stack size

- Fixed behavior of `DO TURNOVERN` with an argument of 0

- Fixed behavior of `CONTROL B` and `CONTROL RETURN` when not nested
- The output buffer is now flushed every 0.5 seconds

- Added `--debug` option to CLI, for displaying stack/heap contents after program execution
- Added `BespokeInterpreter.from_file()` method
- Fixed bug where `Specifier was expected, but none found` would not show the command which expected a specifier
- Fixed behavior of `STACKTOP POW` with a second argument of 0
- `BespokeInterpreter` no longer writes error message to STDERR when used as a context manager
- Many properties of `BespokeInterpreter` objects are now private, or have getters/setters
- CLI now handles file-opening errors