Drag 'n Drop example is broken about flyd

[nordfjord]

This has to do with takeUntil

const s1 = stream(1)
const s2 = stream(2)

const s3 = takeUntil(s1, s2)

s3().end() // true

The stream is immediately ended if s2 has a value

Internally in the switch-latest module we use

const dropCurrentValue = flyd.transduce(R.drop(1));

To drop 1 value from the stream to prevent this.

A more comprehensive fix is included in #175, but since the fix is not dependent on the rest of the changes in #175 I might just pop it out of there and make another PR for that.

The fix there is in the takeUntil module:

const dropCurrentValue = flyd.transduce(drop(1));
function takeUntil(src, term) {
  const end$ = flyd.merge(term.hasVal ? dropCurrentValue(term) : term, src.end);
  // ...
}

[hbarcelos]

Thank's a lot @nordfjord. Will this PR be merged any time soon?