* tests: really check that a parse that should succeed does indeed return a Match, rather than only check that it doesn't die
* reset state of Tracer on calls to parse/subparse and parsefile (thus providing a first fix for #5)
  However, it's a) still a lot of code dup and b) state is still associated with meta-class (which is not correct)
* fix: re-enable tracer.t (sorry)