Merge branch 'development'

* development:
  SocketAckEmitter.isExpected => .expected
  change isRequired() to isExpected()
  remove semicolon
  add SocketAckEmitter.isRequired()
  fix Use Legacy Swift issue

Socket.IO-Client-Swift.podspec

@@ -17,5 +17,6 @@ Pod::Spec.new do |s|
   s.source       = { :git => "https://github.com/socketio/socket.io-client-swift.git", :tag => 'v8.1.0' }
   s.source_files  = "Source/**/*.swift"
   s.requires_arc = true
+  s.pod_target_xcconfig = {'SWIFT_VERSION' => '3.0'}
   # s.dependency 'Starscream', '~> 0.9' # currently this repo includes Starscream swift files
 end

Source/SocketAckEmitter.swift

@@ -27,6 +27,10 @@ import Foundation
 public final class SocketAckEmitter : NSObject {
     let socket: SocketIOClient
     let ackNum: Int
+
+    public var expected: Bool {
+        return ackNum != -1
+    }
     
     init(socket: SocketIOClient, ackNum: Int) {
         self.socket = socket
@@ -44,6 +48,7 @@ public final class SocketAckEmitter : NSObject {
         
         socket.emitAck(ackNum, with: items)
     }
+        
 }
 
 public final class OnAckCallback : NSObject {