Display paths properly in gallery

* use __ rather than _ as the ‘dummy’ separator char,
  as it is much less commonly used than _ in a
  file/directory name
* replace __ with / when displaying paths in the gallery
Remove puts, which appear to generate blank lines in console log
Merge pull request #158 from pmuir/remove_blank_lines

Remove puts, which appear to generate blank lines in console log
Merge pull request #156 from pmuir/paths

Paths
Add a mode flag, allows sorting/hiding by difference size

Fixes #153