updated nuget and nuspecs for 2.0.0
fix #39 start package Initialize()
update nuget urls
fix #41 by adding DataContractAttribute to PropertyChangedBase
Allow Navigation Service to handle hardware back button. Fixes #42
Remove underlying exception in SettingsService. Fixes #48
Don't use LayoutUpdated sender. Fixes #56
Convention for WP8.1 Pivot. Fixes #65
make ActionMessage.ApplyAvailabilityEffect more robust to null values (#47)
add caliburn.micro as submodule
Allow inheritors to initialize Screen
PropertyChangedBase option for disabling notifications on Ui Thread