Made swift package

Merge pull request JohnSundell#177 from JohnSundell/swift-4.1-bad-acc…

…ess-fix

Event: Fix Bad Access crash when using Swift 4.1

Merge pull request JohnSundell#159 from JohnSundell/xcode-templates

Add Xcode template

CameraTests: Remove whitespaces

Merge pull request JohnSundell#96 from JohnSundell/actor-added-remove…

…d-events

Scene: Add events for when an actor is added or removed

Merge pull request JohnSundell#76 from JohnSundell/xcpretty

CI: Use xcpretty to format xcodebuild output

Merge pull request JohnSundell#40 from JohnSundell/plugin-return-exis…

…ting-instance

Plugins: Return existing instance when adding a plugin

Actor: Document that scale now affects collision detection

Merge pull request JohnSundell#30 from JohnSundell/tutorial-2

Documentation: Add 2nd tutorial

README: Update for macOS support