Create test helper for unhandled rejections
Create test helper for unhandled rejections

Since Mocha ignores these by default, convert unhandledRejections into
unhandledExceptions so Mocha will fail the test which caused them.

Signed-off-by: Kevin Locke <ffb4761cba839470133bee36aeb139f58d7dbaa9@kevinlocke.name>

kevinoid/stream-compare,kevinoid/stream-compare,kevinoid/stream-compare