v2.0.0 Interval based scheduler

• Renamed Schedule to Cron
• New IntervalBasedScheduler
• Moved setTimeout, setInterval and clearTimeoutOrInterval to TimerBasedScheduler

See README.md for instructions on how to use the new scheduler.

Quick migration guide:

// v1.x
import { parseCronExpression } from 'cron-schedule'

const schedule = parseCronExpression('* * * * *')
schedule.setTimeout(fn)
schedule.setInterval(fn)
schedule.clearTimeoutOrInterval(id)


// v2.x
import { parseCronExpression, TimerBasedScheduler as scheduler } from 'cron-schedule'

const cron = parseCronExpression('* * * * *')
scheduler.setTimeout(cron, fn)
scheduler.setInterval(cron, fn)
scheduler.clearTimeoutOrInterval(id)