(Issue #3715) Add spacer element to control margin/padding
(Issue #3715) added comments to zooming
(Issue #3715) adjusted spacing
(Issue #3715) better ascii art
(Issue #3715) cache margin calculation to avoid scaling all pages on new page load
(Issue #3715) cleanup
(Issue #3715) Handle out-of-order xhr completions
(Issue #3780) Restrict upload new version to a single file
(Issue #3781) Ensure uploaded file(s) have actual content
(Issue #3781) More general approach
(Issue #3715) followup from review
(Issue #3780) add error messages when uploading not possible
(Issue #3781) Add error message when no content identified
fix additional problems with dropzone-based uploads
(Issue #3715) Adjust docs on method
(Issue #3780) consolidate error messages
(Issue #3781) modify error messages
(Issue #3781) handle dropped folders (and files) in Chrome
add more forgiving error handling
(Issue #3781) trigger event in all cases (so error message may be displayed)