Try out single random source
Reuse image.Rect in grid gen
Implement an Icon pool
Revert "Try out single random source"

This reverts commit fcfb7e225a13f3e9c6b2308b7e2fe5d3af7678f8.

Conflicts:
	ricons.go
Merge branch 'optimize'

Leaving the history untouched.
Revise README.md
Version bump to 0.0.2