Added SendingMessage event to Xamarin.Android provider.
Proper Xamarin.Android test project.
Added SendingMessage event to Xamarin.iOS provider.
Fixed new Xamarin.iOS unit tests.
Added SendingMessage event to WindowPhone provider.
Added SendingMessage event to WinRT provider.
Added SendingMessage event to WindowsStore provider.
Merge pull request #171 from MindscapeHQ/SendingMessage-event

Sending message event