Repair Test::Class for Test::Builder1.5

Results are no longer stored by default to save memory.  There are
better ways to get test statistics.  Use them if available.
Fix tests for the new TAP version header and minor format changes.

Throw out the TAP header and normalize how "# SKIP" is formatted.
This is compatible with 0.x and 1.5.
Fix t/skip2.t for Test::Builder1.5.

Test::Builder 1.5 made minor changes to the TAP format which makes testing
via string equality difficult.  Using Test::Builder::Tester mitigates some
of that.

Testing inside the exit handler allows us to test the output of SKIP_ALL
without a lot of piping things around and still being able to take
advantage of Test::Builder::Tester.
Merge pull request #2 from schwern/bug/TB1.5

Fix Test::Class for Test::Builder 1.5