More API additions and improvements!

• API Additions
  • Whether or not a focused node can be moved
  • Spawn area customization
  • Rotation speed customization
  • Determine if a node is being focused through isFocusing
  • The scene behind the view is now exposed for developers who want to delve deep into SpriteKit
• Other
  • Selected nodes that are tapped again now inform the client
  • Added extra scaling animation to the default node style
  • Refined the focus animation