Update stacktraceplus dependency.

commit b1592cd5c2a6f77b952a4ae3daff5a14dedf16a9
Author: Ignacio Burgueño <ignaciob@inconcertcc.com>
Date:   Mon Jun 2 15:38:32 2014 -0300

    Improve test runner

    The test runner was not reporting errors correctly.
    The error code wasn't being propagated.