there's some serious duplication here with this default parameterised methods with the completion handler

Duplication

class ApiManager {
  class func GET(
        URLString: URLStringConvertible,
        parameters: [String : AnyObject]? = nil,
        encoding: ParameterEncoding? = .URL,
        headers: [String : String]? = nil,
        completionHandler: CompletionHandlerType
        ){
            alamofireManager().request(.GET, URLString, parameters: parameters, encoding: encoding!, headers: headers)
                .validate()
                .responseJSON  {
                    response in
                    switch response.result {
                    case .Success(let JSON):
                        completionHandler(result: .Success(response: JSON, statusCode: response.response!.statusCode))
                        
                    case .Failure(_):
                        completionHandler(result: .Failure(error: response.result.error!, statusCode: response.response!.statusCode))
                    }
            }
    }
    
    class func POST(
        URLString: URLStringConvertible,
        parameters: [String : AnyObject]? = nil,
        encoding: ParameterEncoding? = .URL,
        headers: [String : String]? = nil,
        completionHandler: CompletionHandlerType
        ){
            alamofireManager()
                .request(.POST, URLString, parameters: parameters, encoding: encoding!, headers: headers)
                .validate()
                .responseJSON  {
                    response in
                    switch response.result {
                    case .Success(let JSON):
                        completionHandler(result: .Success(response: JSON, statusCode: response.response!.statusCode))
                        
                    case .Failure(_):
                        completionHandler(result: .Failure(error: response.result.error!, statusCode: response.response!.statusCode))
                    }
            }
            
    }
    class func PUT(
        URLString: URLStringConvertible,
        parameters: [String : AnyObject]? = nil,
        encoding: ParameterEncoding? = .URL,
        headers: [String : String]? = nil,
        completionHandler: CompletionHandlerType
        ){
            alamofireManager().request(
                .PUT, URLString, parameters: parameters, encoding: encoding!, headers: headers)
                .validate()
                .responseJSON {
                    response in
                    switch response.result {
                    case .Success(let JSON):
                        completionHandler(result: .Success(response: JSON, statusCode: response.response!.statusCode))
                        
                    case .Failure(_):
                        completionHandler(result: .Failure(error: response.result.error!, statusCode: response.response!.statusCode))
                    }
            }
    }
    
    
    class func DELETE(
        URLString: URLStringConvertible,
        parameters: [String : AnyObject]? = nil,
        encoding: ParameterEncoding? = .URL,
        headers: [String : String]? = nil,
        completionHandler: CompletionHandlerType)
    {
        alamofireManager().request(
            .DELETE, URLString, parameters: parameters, encoding: encoding!, headers: headers)
            .validate()
            .responseJSON {
                response in
                switch response.result {
                case .Success(let JSON):
                    completionHandler(result: .Success(response: JSON, statusCode: response.response!.statusCode))
                    
                case .Failure(_):
                    completionHandler(result: .Failure(error: response.result.error!, statusCode: response.response!.statusCode))
                }
        }
    }
    
  }