Require Swift 4.1; add 4.2 to CI

.travis.yml

@@ -1,39 +1,33 @@
 matrix:
   include:
-    - env: JOB=macOS
+    - language: objective-c
       os: osx
-      osx_image: xcode9.2
-      language: objective-c
+      osx_image: xcode9.4
       install: bundle install --quiet
       script: bundle exec fastlane mac ci
-    - env: JOB=iOS
+    - language: objective-c
       os: osx
-      osx_image: xcode9.3
-      language: objective-c
+      osx_image: xcode10.0
       install: bundle install --quiet
       script: bundle exec fastlane ios ci
       after_failure:
         - cat ~/Library/Developer/Xcode/DerivedData/Deferred-*/Logs/Test/*/Session-MobileDeferredTests-*.log | true
         - cat ~/Library/Logs/scan/Deferred-*.log | true
-    - env: JOB=Linux SWIFT=4.0
+    - language: generic
       os: linux
       dist: trusty
       sudo: required
-      language: generic
-      install:
-        - echo "4.0" > .swift-version
-        - eval "$(curl -sL https://swiftenv.fuller.li/install.sh)"
+      env: SWIFT_VERSION=4.1
+      install: eval "$(curl -sL https://swiftenv.fuller.li/install.sh)"
       script:
         - swift --version
         - swift test --parallel
-    - env: JOB=Linux SWIFT=4.1
+    - language: generic
       os: linux
       dist: trusty
       sudo: required
-      language: generic
-      install:
-        - echo "4.1" > .swift-version
-        - eval "$(curl -sL https://swiftenv.fuller.li/install.sh)"
+      env: SWIFT_VERSION=4.2-DEVELOPMENT-SNAPSHOT-2018-09-14-a
+      install: eval "$(curl -sL https://swiftenv.fuller.li/install.sh)"
       script:
         - swift --version
         - swift test --parallel

Documentation/Guide/Getting Started.md

@@ -43,11 +43,12 @@ Then run `pod install`.
 
 ### Swift Package Manager
 
-We include support for [Swift Package Manager](https://swift.org/package-manager/) on 3.x toolchains.
+We include support for [Swift Package Manager](https://swift.org/package-manager/) on 4.1 or greater toolchains.
 
 Add us to your `Package.swift`:
 
 ```swift
+// swift-tools-version:4.0
 import PackageDescription
 
 let package = Package(

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:4.0
+// swift-tools-version:4.1
 
 //
 //  Package.swift
@@ -31,5 +31,4 @@ let package = Package(
             name: "TaskTests",
             dependencies: [ "Deferred", "Task" ],
             exclude: [ "Tests/AllTestsCommon.swift" ])
-    ],
-    swiftLanguageVersions: [ 4 ])
+    ])

README.md

@@ -8,7 +8,7 @@ Deferred is a "futures library", probably like ones you've already heard about.
 
 |                                                                                                        |
 |--------------------------------------------------------------------------------------------------------|
-|[![Swift 3.x](https://img.shields.io/badge/swift-4.x-EF5138.svg)][Swift]                                |
+|[![Requires Swift 4.1 or greater](https://img.shields.io/badge/swift-4.1%2B-EF5138.svg)][Swift]         |
 |[![Under MIT License](https://img.shields.io/badge/license-MIT-blue.svg)][MIT]                          |
 |![Multiplatform](https://img.shields.io/badge/platforms-macOS,_iOS,_watchOS,_tvOS,_Linux-lightgrey.svg) |
 |[![Travis CI](https://img.shields.io/travis/bignerdranch/Deferred.svg)][CI]                             |