Generalize EventStream methods to Property

[raimohanska]

• flatMap
• switch
• startWith : for injecting an Init value, same as toProperty(initValue)
• mapEnd
• scan (in progress, issue 17)

Possibly add

• toEventStream: makes an event stream that's like p.changes().startWith(p.currentValue)

[mtkopone]

Nom nom... Yes please. Here's what we currently have:

Bacon.Property.prototype.switch = function(fn) {
  var changes = this.changes()
  return this.flatMap(function(value) {
    return fn(value).takeUntil(changes)
  })
}
Bacon.Property.prototype.flatMap = function() {
  return Bacon.EventStream.prototype.flatMap.apply(this, arguments)
}
Bacon.Property.prototype.takeUntil = function() {
  return Bacon.EventStream.prototype.takeUntil.apply(this, arguments)
}

Not entirely sure that it works tho...

[raimohanska]

• takeUntil is already implemented in the Observable class.
• flatMap can be simply moved to Observable
• switch could be as above, or like @toEventStream().switch(..).

[raimohanska]

Who wants to do this? Most work is writing tests, probably. Docs should be updated as well.

[raimohanska]

Done with flatMap: 3957ea7

[raimohanska]

Done with switch, toEventStream: d307010

[raimohanska]

Readme updated in a6573d6