Collapse errors into a single list; partially solves issue #6.

Rather than issue a list of {error, Reason} we now issue {error, [Reason]}. The
change is relatively minor but makes matching somewhat simpler.

Signed-off-by: Brian L. Troutwine <brian@troutwine.us>
Merge pull request #11 from blt/collapse_errors

Collapse errors into a single list; partially solves issue #6.