Fix silent parser bug on incomplete parsing

What was really missing here was the check of the final
  Ragel state against _first_final.  I've also added a heuristic
  that probably correctly warns about the specific case of the
  missing final newline the vast majority of the time, although
  I'm not 100% certain.  Worst case they still get a more-generic
  error.

Note the sam ebug was also present in the vscf scanner, so I've
  fixed it there as well.

Fixes #57