Allow programmer to ask to stop on first failure. 

Many times when I run a test suite what I want is to stop at the first failure. For example when installing modules from CPAN, CPAN will by default not install if there is *any* failure, so you may as well save time and stop after the first failure. 

To first approximation it seems pretty easy to add this. I mean like one or two lines of Perl code. (testing and documentation not included in this count..) In the merge request code, set environment variable `TEST_MORE_BAIL_EARLY`. 

The forked repository also has the corresponding code for the Test-Builder-1.5 branch as well. The test code however I've not been able to work out yet. 

Also I haven't updated the documentation to mention this. However if the approach and code seems reasonable, I'll add and update the merge request.