Fix the migration link to make it not relative to the current page (#108)

Author: SMJSGaming

tutorials/events.md

@@ -1,6 +1,6 @@
 # Events
 
-> :warning: This section of the documentation is currently out of date. Please see [the v5 migration guide](tutorials/migrate-v5) for differences required for Geode v5.
+> :warning: This section of the documentation is currently out of date. Please see [the v5 migration guide](/tutorials/migrate-v5) for differences required for Geode v5.
 
 For most things in GD, such as `CCTextInputNode`, GD and Cocos2d-x use a **delegate-based event system**, where you install a delegate on the target class, and the delegate receives events via overridden virtual functions. This system works fine for most situations, but is often quite clumsy to use and runs into a few important issues: you have to manually deal with removing the delegate if the target class outlives the delegate, and more importantly, you can only have one delegate per target.