Merge branch 'master' into release

Author: kzaher

Documentation/GettingStarted.md

@@ -880,7 +880,7 @@ The reason why 2 navigations are suggested is because first navigation forces lo
 
 `Variable`s represent some observable state. `Variable` without containing value can't exist because initializer requires initial value.
 
-Variable wraps a [`Subject`](http://reactivex.io/documentation/subject.html). More specifically it is a `BehaviorSubject`.  Unlike `BehaviorSubject`, it only exposes `value` interface, so variable can never terminate or fail.
+Variable wraps a [`Subject`](http://reactivex.io/documentation/subject.html). More specifically it is a `BehaviorSubject`.  Unlike `BehaviorSubject`, it only exposes `value` interface, so variable can never terminate with error.
 
 It will also broadcast its current value immediately on subscription.
 

README.md

@@ -3,6 +3,9 @@
 
 [![Travis CI](https://travis-ci.org/ReactiveX/RxSwift.svg?branch=master)](https://travis-ci.org/ReactiveX/RxSwift) ![platforms](https://img.shields.io/badge/platforms-iOS%20%7C%20macOS%20%7C%20tvOS%20%7C%20watchOS%20%7C%20Linux-333333.svg) ![pod](https://img.shields.io/cocoapods/v/RxSwift.svg) [![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage) [![Swift Package Manager compatible](https://img.shields.io/badge/Swift%20Package%20Manager-compatible-brightgreen.svg)](https://github.com/apple/swift-package-manager)
 
+* RxSwift 4.x / Swift 4.x can be found in [**rxswift4.0-swift4.0** branch](https://github.com/ReactiveX/RxSwift/tree/rxswift4.0-swift4.0).
+* RxSwift 3.x / Swift 3.x can be found in [**master** branch](https://github.com/ReactiveX/RxSwift/tree/master).
+
 Rx is a [generic abstraction of computation](https://youtu.be/looJcaeboBY) expressed through `Observable<Element>` interface.
 
 This is a Swift version of [Rx](https://github.com/Reactive-Extensions/Rx.NET).

RxSwift/Schedulers/CurrentThreadScheduler.swift

@@ -50,7 +50,11 @@ public class CurrentThreadScheduler : ImmediateSchedulerType {
 
     private static var isScheduleRequiredKey: pthread_key_t = { () -> pthread_key_t in
         let key = UnsafeMutablePointer<pthread_key_t>.allocate(capacity: 1)
-        if pthread_key_create(key, nil) != 0 {
+        defer {
+            key.deallocate(capacity: 1)
+        }
+                                                               
+        guard pthread_key_create(key, nil) == 0 else {
             rxFatalError("isScheduleRequired key creation failed")
         }