fixes #31 allows to run the game in the newest xcode beta
Merged in Chris' XCode fixes into my huge update.

With this, it will compile on both (beta4 and beta5) with one tiny exception. On Beta5, you'll get a complaint about _bridgeToObjectiveC in ImageTools.swift. Just remove the leading underscore.

Merge branch 'hallas/beta6-fixes' of https://github.com/jocelynlih/SwiftGameBook into paul

Conflicts:
	PencilAdventure/PencilAdventure/GameScene.swift
	PencilAdventure/PencilAdventure/ImageTools.swift
	PencilAdventure/PencilAdventure/LevelSelectScene.swift
	PencilAdventure/PencilAdventure/SketchRender.swift