Changelog for drifter-0.2.1

# 0.2.1 * Fix bug where changeSequence would drop the head of the list. # 0.2 * Drop direct support for postgresql. That can be found in the drifter-postgresql package. * Just export a single module, Drifter * Change Drifter typeclass method from migrate to migrateSingle * Add changeSequence helper function * Make migrate automatically resolve dependency order