title: error after updating the Xcode to 7.0
body: <p>I'm developing an iOS application in Swift.
  When I updated the Xcode to 7.0, I'm getting error in swiftyJSON.</p>
  
  <pre><code> static func fromObject(object: AnyObject) -&gt; JSONValue? {
      switch object {
      case let value as NSString:
          return JSONValue.JSONString(value as String)
      case let value as NSNumber:
          return JSONValue.JSONNumber(value)
      case let value as NSNull:
          return JSONValue.JSONNull
      case let value as NSDictionary:
          var jsonObject: [String:JSONValue] = [:]
          for (k:AnyObject, v:AnyObject) in value {// **THIS LINE- error: "Definition conflicts with previous value"**
              if let k = k as? NSString {
                  if let v = JSONValue.fromObject(v) {
                      jsonObject[k] = v
                  } else {
                      return nil
                  }
              }
          }
  </code></pre>
  
  <p>What's the problem? Can you help, please?</p>