Breaking change from v2.0.0 to v2.1.0
This project seems cursed with semver and npm tagging misuse.

Koa v2.0.1 supported node v4 and above. However, Koa v2.1.0 does not support node v4 and 5. Therefore, koa v2.1.0 introduced a breaking change and should have been released as koa v3.0.0.

My app (which depends on koa@^2.0.0)  started breaking overnight on node v4 and v5 (after koa v2.1.0 was released) - obviously this should never happen where semantic versioning is adhered to. 