Updated README - App Builder Tutorial

Added a link to the XPCK App Builder tutorial to the README.
Merge pull request #32 from mikescott8/master

updated ignore for .DotSettings
Fallback to logo when image not found in RSS item
Merge branch 'master' of https://github.com/winappkits/XPlatformCloudKit
Add Youtube Author example
Merge pull request #34 from acrow59/master

Updated README - App Builder Tutorial