Feature/34: rewrite all unit tests for md->CLIP converter

[EmilyGraceSeville7cf]

closes #34

Unit tests are written for:

• [x] CLI
• [x] summary conversion
• [x] example description
• [x] placeholders:
  • [x] empty ellipsis
  • [x] special placeholder conversions: can't fix some cases (see #85 for more details)
  • [x] integer
  • [x] float
  • [x] option
  • [x] device
  • [x] path
  • [x] file
  • [x] directory
  • [x] boolean
  • [x] character
  • [x] sample file