Add additional test for daylight savings glitch

The problem was that clocks go forward *at* 2am, so
2am doesn't exist once a year. Users might be surprised
that their cron trigger doesn't go off one night, but that
is arguably correct (and what happens now). The test can be
modified if we decide to change the trigger behaviour.
Merge pull request #251 from dsyer/feature/crontest

# By Dave Syer
* dsyer-feature/crontest:
  Add additional test for daylight savings glitch