feat/bug: Reject when function is async but not done called nor Promise returned

[tunnckoCore]

Almost the same as #18

if (isAsyncFn && !called && !isPromise(syncResult)) {
  var msg = 'async function need to call `done/cb` callback argument or return a Promise'
  reject(new Error('redolent: ' + msg))
}

for example

var fn = redolent(function (foo, done) {
  console.log('foo is', foo)
  // done is not called nor Promise is returned,
  // so when `fn` is called it will return rejected promise 
})

fn(123).catch(console.log)

[tunnckoCore]

Not so easy and probably is tricky.

But another thing is found. Should return rejected error when done is not called but returns a non Promise value (it can return and return undefined)