Enhancements:

- file URL now starts with "file://" (standard) rather than "file:"
- new optional argument 'context' to enable()
- repeated variable names don't have their values shown twice
- dotted attributes are shown; missing attributes handled reasonably
- highlight the whole logical line even if it has multiple physical lines
- use nice generator interface to tokenize
- formatting fixed so that it looks good in lynx, links, and w3m too