update initialize dependency

pubspec.yaml

diff --git a/pubspec.yaml b/pubspec.yaml
index 2fea43f..672193e 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -11,7 +11,7 @@
   bundle code and HTML as if they were libraries.
 dependencies:
   html5lib: '>=0.12.0 <0.13.0'
-  initialize: '>=0.2.0 <0.3.0'
+  initialize: '>=0.3.0 <0.4.0'
   path: '>=1.3.0 <2.0.0'
 dev_dependencies:
   unittest: '>0.11.0 <0.12.0'