fix compile error in case insensitive system

Author: bryan.wu

lib/src/EnhancedEventEmitter.dart

@@ -2,7 +2,7 @@ import 'dart:async';
 
 import 'package:events2/events2.dart';
 
-import 'Logger.dart';
+import 'logger.dart';
 
 Logger _logger = Logger('EnhancedEventEmitter');
 

lib/src/message.dart

@@ -1,7 +1,7 @@
 import 'dart:convert';
 
-import 'Logger.dart';
-import 'Utils.dart' as utils;
+import 'logger.dart';
+import 'utils.dart' as utils;
 
 final logger = new Logger('Message');
 

lib/src/transports/NativeTransport.dart

@@ -1,8 +1,8 @@
 import 'dart:convert';
 import 'dart:io';
 
-import '../Logger.dart';
-import '../Message.dart';
+import '../logger.dart';
+import '../message.dart';
 import 'TransportInterface.dart';
 
 final _logger = Logger('Logger::NativeTransport');

lib/src/transports/WebTransport.dart

@@ -1,8 +1,8 @@
 import 'dart:convert';
 import 'dart:html';
 
-import '../Logger.dart';
-import '../Message.dart';
+import '../logger.dart';
+import '../message.dart';
 import 'TransportInterface.dart';
 
 final _logger = Logger('Logger::WebTransport');