Update BitSet to Swift 4.2

Author: sticksen

Bit Set/BitSet.playground/Contents.swift

@@ -1,10 +1,5 @@
 //: Playground - noun: a place where people can play
 
-// last checked with Xcode 9.0b4
-#if swift(>=4.0)
-print("Hello, Swift 4!")
-#endif
-
 // Create a bit set that stores 140 bits
 var bits = BitSet(size: 140)
 

Bit Set/BitSet.playground/contents.xcplayground

@@ -1,4 +1,4 @@
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<playground version='5.0' target-platform='osx'>
+<playground version='5.0' target-platform='osx' last-migration='1000'>
     <timeline fileName='timeline.xctimeline'/>
 </playground>

Bit Set/BitSet.playground/playground.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>