Implement Image Stitching Infrastructure

Stitching Infrastructure was implemented from (algorithmix/stitch).
Added a way to

- Stitch Shreds
- Export Clusters
- Flatten nodes
- Naive Stitch (no horizontal offsets)
Remove PNG - Ignore in gitignore
Readme change
Bumpversion
update tests
Merge pull request #6 from Algorithmix/stitching

Stitching