Update to Swift 4.2

Author: hisaac

.swift-version

@@ -1 +1 @@
-4.1
+4.2

Package.resolved

@@ -1,4 +1,4 @@
-// swift-tools-version:4.1
+// swift-tools-version:4.2
 
 /**
  *  ShellOut

Package.swift

@@ -15,13 +15,15 @@ print(output) // Hello world
 ```
 
 You can also easily run a series of commands at once, optionally at a given path:
+
 ```swift
 try shellOut(to: ["mkdir NewFolder", "echo \"Hello again\" > NewFolder/File"], at: "~/CurrentFolder")
 let output = try shellOut(to: "cat File", at: "~/CurrentFolder/NewFolder")
 print(output) // Hello again
 ```
 
 In case of an error, ShellOut will automatically read `STDERR` and format it nicely into a typed Swift error:
+
 ```swift
 do {
     try shellOut(to: "totally-invalid")