Indicate if tests don't go to plan

One of the major features of TAP is that you have a test plan.
If my TAP starts 1..100, but only 5 results are recorded before something broke, then I want to know about it. Likewise, if 105 results are recorded, I want some kind of error indication.

I suggest counting this as 95 skipped tests by default, possibly with an config option to treat them as failed instead.