Merge pull request #777 from varun989/master

[Swift 4.2] Update LinkedList

Author: richard-ash

Linked List/LinkedList.playground/contents.xcplayground

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