update version, readme and changelog

CHANGELOG.md

 # CHANGELOG
 
+## 0.3.4+1
+
+fix:
+
+- title and left icon color.
+- checkColor in preview can be edit.
+
 ## 0.3.4
 
 rollback `photo_manager` to `0.3.4`

README.md

       checkBoxBuilderDelegate: DefaultCheckBoxBuilderDelegate(
         activeColor: Colors.white,
         unselectedColor: Colors.white,
+        checkColor: Colors.blue,
       ), // default is DefaultCheckBoxBuilderDelegate ,or you make custom delegate to create checkbox
 
       loadingDelegate:

pubspec.yaml

 name: photo
 description: image picker, multi picker support video/icloud asset, use flutter as ui, if you want to build custom ui, you just use photo_manager.
-version: 0.3.4
+version: 0.3.4+1
 author: caijinglong<cjl_spy@163.com>
 homepage: https://github.com/CaiJingLong/flutter_photo
 
 environment:
-  sdk: ">=2.0.0-dev.68.0 <3.0.0"
+  sdk: '>=2.0.0-dev.68.0 <3.0.0'
 
 dependencies:
   flutter: