Add bufferWithTimeout() and bufferWithInterval().

Highland uses setTimeout() and Kefir uses setInterval() for the batch/buffer with time (illustrated below). It would be nice to have both functions in Kefir, with a distinctive name.

Using highlandStream.batchWithTimeOrCount(100 /*ms/*, Infinity):

[ 0, 0, 0 ]
[ 150, 200, 250 ]
[ 300, 350, 400 ]

Using kefirStream.bufferWithTimeOrCount(100 /*ms*/, Infinity):

[ 0, 0, 0 ]
[ 150 ]
[ 200, 250 ]
[ 300, 350 ]
[ 400 ]

[rpominov]

Yeah, if we subscribe to the same stream twice here is how it can be done:

var stream = Kefir.stream(em => {
  setTimeout(() => {em.value(0); em.value(0); em.value(0)}, 0)
  setTimeout(() => {em.value(150)}, 150)
  setTimeout(() => {em.value(200)}, 200)
  setTimeout(() => {em.value(250)}, 250)
  setTimeout(() => {em.value(300)}, 300)
  setTimeout(() => {em.value(350)}, 350)
  setTimeout(() => {em.value(400); em.end()}, 400)
})

stream.bufferBy(stream.flatMapFirst(() => Kefir.later(100))).log()

[rpominov]

Yea, I just not 100% sure about Flow/TypeScript, but I’ll merge the PR if you create one.