removing trace properties from Request
adapt to the change of Request.withException constructor
add view.dart
adding toMap() to Document
change type of content to dynamic, also add local var newContent at send(), because we cannot modify content
adding DetailView
adding ListView
adding usable/detail_view.dart and usable/list_view.dart to lib
override toString() so when there're error, it display the error message
added _TemplateView and fix error message for the args on Http500 class
make transformer dynamic
removing Request.trace from test, because .trace is now gone from Request
adding use case to simulateServer() when we give transformer
adding view_test.dart
just adding a space