Requested by @spf13 and @extemporalgenome.

@spf13: on linux at least, all you need to do the proper tracking of vim/any-other-kind-of-editor "done writing" tracking is watch for IN_CLOSE_WRITE and IN_MOVE_TO on the directory

@extemporalgenome if it's a lazy editor, that just updates in place, IN_CLOSE_WRITE catches it; if it's a "write to temporary and atomically rename" editor, IN_MOVE_TO catches it

The trouble is in doing this in a cross-platform way. And some users may still want IN_MODIFY (eg. to show the progress of a file writing).