Pull out all the string constants in AnimationFactory

Something is probably wrong with the SwiftyJson:

In SwiftyJson 2.2.1,

private struct JsonIdentifier {
  static let Type = "type"
}

let IdentifierType = "type"
let type = json["type"].string // compile ok
let type = json[IdentifierType].string // compile ok
let type = json[JsonIdentifier.Type].string // compile error

ocadotechnology / codeforlife-ios

Pull out all the string constants in AnimationFactory #41