I have an iPhone 6 Plus with iOS 8.3. I have been using a version of PlainText (the app) from several years ago, and it is broken in several ways but it is still the best thing I have found. I want a text editor that can edit plain text files stored in Dropbox. Ideally, I want it to sync to just a subdirectory of Dropbox, not the entire folder (PlainText used to have this feature). It needs to sync to Dropbox, other cloud storage services need not apply. Thank you.