Fix Web build

@@ -26,7 +26,9 @@ import 'package:meta/meta.dart';
 import 'package:utf/utf.dart';
 import 'package:vector_math/vector_math_64.dart';
 
-import 'src/io.dart' if (dart.library.io) 'src/archive.dart';
+import 'src/io.dart'
+    if (dart.library.io) 'src/io_vm.dart'
+    if (dart.library.js) 'src/io_archive.dart';
 
 part 'src/annotation.dart';
 part 'src/array.dart';

-import 'package:archive/archive.dart';
-
-import 'package:pdf/pdf.dart';
-
-DeflateCallback defaultDeflate = ZLibEncoder().encode;

-import 'dart:io';
+/*
+ * Copyright (C) 2017, David PHAM-VAN <dev.nfet.net@gmail.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 
 import 'package:pdf/pdf.dart';
 
-DeflateCallback defaultDeflate = zlib.encode;
+DeflateCallback defaultDeflate;

+/*
+ * Copyright (C) 2017, David PHAM-VAN <dev.nfet.net@gmail.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import 'package:archive/archive.dart';
+
+import 'package:pdf/pdf.dart';
+
+DeflateCallback defaultDeflate = ZLibEncoder().encode;

+/*
+ * Copyright (C) 2017, David PHAM-VAN <dev.nfet.net@gmail.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import 'dart:io';
+
+import 'package:pdf/pdf.dart';
+
+DeflateCallback defaultDeflate = zlib.encode;