Added comments to document changes reasons

Author: OneSman7

Source/SocketIO/Engine/SocketEngine.swift

@@ -359,6 +359,7 @@ open class SocketEngine : NSObject, URLSessionDelegate, SocketEnginePollable, So
     ///
     /// **You shouldn't call this directly**
     open func doFastUpgrade() {
+        
         if waitingForPoll {
             DefaultSocketLogger.Logger.error("Outstanding poll when switched to WebSockets," +
                 "we'll probably disconnect soon. You should report this.", type: SocketEngine.logType)
@@ -371,7 +372,10 @@ open class SocketEngine : NSObject, URLSessionDelegate, SocketEnginePollable, So
         fastUpgrade = false
         probing = false
         flushProbeWait()
-        if postWait.count != 0 {
+        
+        // Need to flush postWait to socket since it connected successfully
+        // (moved from flushProbeWait() since it is also called on connected failure)
+        if !postWait.isEmpty {
             flushWaitingForPostToWebSocket()
         }
     }

Source/SocketIO/Manager/SocketManager.swift

@@ -168,7 +168,10 @@ open class SocketManager : NSObject, SocketManagerSpec, SocketParsable, SocketDa
         DefaultSocketLogger.Logger.log("Adding engine", type: SocketManager.logType)
 
         engine?.engineQueue.sync {
+            
             self.engine?.client = nil
+            
+            // Close old engine so it will not leak because of URLSession if in polling mode
             self.engine?.disconnect(reason: "Adding new engine")
         }