Renamed RIModel to RIDownloadController.
Delete DropboxSample
Implemented reload user home timeline
Merge branch 'feature/download-controller' into develop

Conflicts:
	IronKit/RIModel.h
	IronKit/RIModel.m
	Samples/DropboxSample/DropboxSample.xcodeproj/project.pbxproj
	Samples/DropboxSample/DropboxSample/DBFetchModel.m
	Samples/DropboxSample/DropboxSample/DBUploadModel.m