Roll back version 2.1.0

Sorry it took me a few days to get to this. I unpublished 3.0.0 from npm since no one can use it as-is, I bumped the version to 2.1.0, and I published that to npm. This change set is just for the version rollback.

Fixes https://github.com/bobobo1618/docpad-plugin-sunny/issues/14