2.27.0

 * Remove sl-blip from dependency (Candy)
 * Fix race condition in replication tests (Miroslav Bajtoš)
 * test: remove errant console.log from test (Ryan Graham)
 * Promisify Model Change (Jue Hou)
 * Fix race condition in error handler test (Miroslav Bajtoš)
 * Travis: drop iojs, add v4.x and v5.x (Miroslav Bajtoš)
 * Correct JSDoc findOrCreate() callback in PersistedModel (Miroslav Bajtoš)
 * Hide verificationToken (Miroslav Bajtoš)
 * test: use ephemeral port for e2e server (Ryan Graham)
 * test: fail on error instead of crash (Ryan Graham)
 * ensure app is booted before integration tests (Ryan Graham)
 * Checkpoint speedup (Amir Jafarian)
 * Pull in API doc fix from PR into master #1910 (crandmck)
