Downgrade sinon to 4.5.0
Downgrade sinon to 4.5.0

I hadn't realized 5.0.0 is pre-release.  Use the latest release.

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

kevinoid/travis-status,kevinoid/travis-status,kevinoid/travis-status