iKML v0.1.1

Fixes from the independent review of 0.1.0.

• New error kmz-unsafe-path: a file inside a KMZ whose name would unpack
  outside the folder (../, an absolute path, a drive letter). 0.1.0 only
  noted such a file as unused, and clean copied it into the cleaned KMZ.
  Now clean and convert leave it out, and iKML refuses to write such a
  name into any KMZ.
• New warning kmz-duplicate-entry: two files with the same name in one
  KMZ. iKML keeps the first.
• When bundling a .kml's files into a .kmz, a reference written with
  backslashes is checked after they are turned into slashes, so \x\y.png
  can't become an entry at the archive's root.
• REFERENCE.md and ikml codes no longer lose element names such as
  <kml> when the reference is shown as Markdown.
• The usage text and README said OUT can be -; it can't, since OUT's
  extension picks the format. FILE and IN can be - for standard input.