Refactor code for Swift 1.2.

[inamiy]

This pull request is a BREAKING CHANGE where not only fixing for Swift 1.2 but also refactoring whole codes as follows:

• 1. Rename Signal<T> to Stream<T>
• 2. Stream-operation functions
  • 1. Move functions outside of Stream<T> class for better type-constraints.
  • 2. Rename e.g. merge, mergeAll, mergeInner & always use **All (stream-array) and **Inner (nested-stream) naming conventions
  • 3. Add more useful operations
    • distinct()
    • distinctUntilChanged()
    • reduce()
    • interval()
    • switchLatestInner()
    • prestart() (a.k.a Rx.replay)
    • catch()
    • retry()
    • repeat()
• 3. Add stream pipe operator |> and stream-producer pipe operator |>> in replace of dot-method-chaining syntax.
• 4. Add terminal reacting operator ~>! () to collect synchronously-emitted values (useful just like Java 8 Stream API)
• 5. Update README.md

[DarthMike]

@inamiy First of all, thanks for the lib!

I've got an observation, why do you want to rename Signal to Stream ? Signal already implies stream of values, doesn't it?

[inamiy]

@DarthMike Hi, thanks for question 😄

Though Signal is fairly common term in some languages including ReactiveCocoa in ObjC/Swift, I find Stream is more suitable due to the following reasons:

• ReactKit.Stream is now getting very similar to Java 8 Stream API, matz/streem, and even existing NSInputStream.
• Naming upper & lower streams as upstream & downstream improves (core) code readability ("upsignal" & "downsignal" were not torelable to me 😤)
• Signal (may) confuses with POSIX signal.

And above all, I like the phrase "Everything is a stream" in The introduction to Reactive Programming you've been missing.

[DarthMike]

@inamiy Yes makes sense 👍 Naming is the second hardest problem in programming 😄

[inamiy]

@DarthMike Good to hear you are on this change 😉

[inamiy]

Ready to

[DarthMike]

I've seen new release. Will try later today or tomorrow 🚀 Thanks!

[inamiy]

Thanks too! Any feedback is welcome 😊