support showing download progress for OkHttp
refactored a little bit to allow registration of callbacks
added facade interfaces
added to iOS Network Handler
updated build process to support changes in OkHttp proj
added a missing exception from the facade
updated the facades
style fixups
apparently WeakReferences for delegates don't work in MonoTouch
pull the content-length from the headers
added progress bar to test app
reworked Makefile the vendor folder was keeping the vendor event from running in the Makefile
Fix cancellation in our tests by rigging SendAsync correctly
Style
Merge branch 'progress'

Conflicts:
	src/ModernHttpClient/Facades.cs
	src/ModernHttpClient/ModernHttpClient.iOS.csproj
	src/ModernHttpClient/iOS/NSUrlSessionHandler.cs