Byword, my favorite general-purpose Markdown editor for iOS has been updated today with iOS 8 features that include Document Providers, Handoff, and iCloud Drive. While I can't try Handoff with my Mac and I've yet to figure out if I want to try iCloud Drive, I've tested Document Providers in Byword and they work as advertised. You can open documents from other apps in Byword, edit them, and changes will appear back in the originating app with no Copy or Move operations required. I tested this with TextEdit and Readdle Documents, and it worked perfectly – a nice reminder of how better document management can be on iOS 8 when compared to the old system.
Byword for iOS with the latest iOS 8 features is available on the App Store.