Don't run following tests if setup or topic raise an error
Reporting of errors in setup, topic, teardown
Add new `capture_error` topic decorator which restores old behaviour

Previously, all errors from topic functions were captured and returned
as the topic. Using this decorator on topic functions keeps that
behaviour, otherwise errors in topic functions are reported as errors.
Update tests which relied on old topic error behaviour to use new decorator
Add more comments and tweaks for PR 102
Merge pull request #102 from rcl33/fix-topic-errors

Fix #102 : Failures in `topic` (or `setup`) no longer set the topic value to the error itself.  If this occurs, nested tests aren’t run.  To retain the old behavior, use `@Vows.capture_error` on your topic function.  Thanks to @rcl33 for the fix!