v3.0.0-rc1

Promises land at last, using the pg-promise driver! Everything else hews fairly close to v2.x, although the setAttribute functions have been consolidated into modify, the BETWEEN SQL operation is now supported, and named parameters can be used with run, where, and script files.

This is a release candidate version. If no major issues arise (or if they are easily fixed), I expect to drop 3.0.0 proper sometime in June.