TODO:

     - Unknown callback keys should be fatal.
     - All boolean methods must start with is_ (Aristotle and Paul Johnson)
     - Run it against Perl's test suite (first prove, then tprove).
     - Run Perl::MinimumVersion over it
     - Comments and junk are also allowed *before* the plan.  Sigh.
     - Currently the error messages are not quite as helpful as they could be.
       They could use line and test numbers.
     - Identify junk lines by number.
     - The 'result' objects are currently blessing hashrefs.  This is bad.
       Instead, they should have proper getter/setters to provide future
       support for subclassing.
     - Horrible idea:  have Mac's voice synthesis tell you when tests fail :)
     - Have tprove duplicate all of the functionality of prove.
     - Allow description transformations to be applied.
     - Figure out the namespace.

QUESTIONS:

     - skipped lines should always be OK?  This should be a parse error.
       According to Schwern, this behavior is undefined.
     - VMS 'not' and 'ok' on separate lines?
