creat migration guide for version 1.0.28 (#445)

* Create migrate-1-0-28.md

* Update migrate-1-0-28.md

* Update migrate-1-0-28.md

* Update migrate-1-0-28.md

* Merge from upstream/release/1.0.28

* fix typos

* added "changed network library" to migration guide

Author: fischerscode

docs/migrate-1-0-28.md

@@ -0,0 +1,49 @@
+# Migrate your Flutter application to version 1.0.28
+
+Starting with version 1.0.28, this repository is now separated in a pure dart (parse_server_sdk) and a flutter package (parse_server_sdk_flutter).
+This was done in order to provide a dart package for the parse-server, while keeping maintenance simple.
+You can find both packages in the package directory.
+
+### 1. pubspec.yaml
+In your projects pubspec.yaml at the dependencies section, you have to change
+```
+dependencies:
+    parse_server_sdk: ^1.0.27
+```
+to
+```
+dependencies:
+    parse_server_sdk_flutter: ^1.0.28
+```
+This is the current released version of the parse_server_sdk_flutter package: [![pub package](https://img.shields.io/pub/v/parse_server_sdk_flutter.svg)](https://pub.dev/packages/parse_server_sdk_flutter)
+
+### 2. imports
+As the package name changed, you have to change
+```
+import 'package:parse_server_sdk/parse_server_sdk.dart';
+```
+ to  
+```
+import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
+```
+in every file.
+
+It is recommended to do so by the replacement feature of your IDE.
+
+### optional: provide app information on web
+As flutter web is now in beta, this SDK aims to be web compatible.
+But there are some parts completely different on web. For example, the wep-app cant determine it's name, version or packagename.
+That's why you should provide this information on web.
+```dart
+Parse().initialize(
+    ...
+    appName: kIsWeb ? "MyApplication" : null,
+    appVersion: kIsWeb ? "Version 1" : null,
+    appPackageName: kIsWeb ? "com.example.myapplication" : null,
+);
+```
+
+### changed network library
+In order to provide a `ProgressCallback` for heavy file operations,
+the network library was switched from [http](https://pub.dev/packages/http) to [dio](https://pub.dev/packages/dio).
+There should be no breaking changes regarding this change, except if you are overriding the `ParseHTTPClient`.