update script for gimp 3.0 support

Merge pull request #5 from nerudaj/master

Fix missing arg

Fix #3

Tabs to spaces

Allow to add some spacing between tiles

Merge pull request #2 from schumaml/patch-1

Make tilemancer work on a duplicate of the image

Merge pull request #1 from malteehrlen/add-license-1

Create LICENSE

clarified the donation paragraph

fixed missing display flush

update readme

update links

Add example pics to readme