Enhancements for standard library's cmd module.
Drop-in replacement adds several features for command-prompt tools:
* Searchable command history (commands: "hi", "li", "run") * Load commands from file, save to file, edit commands in file * Multi-line commands * Case-insensitive commands * Special-character shortcut commands (beyond cmd's "@" and "!") * Settable environment parameters * Parsing commands with flags * > (filename), >> (filename) redirect output to file * < (filename) gets input from file * bare >, >>, < redirect to/from paste buffer * accepts abbreviated commands when unambiguous * `py` enters interactive Python console * test apps against sample session transcript (see example/example.py)