Fix #218
What actually slowing down minimap refresh was linear search inside Folds#isFolded() method (that invoked inside nested loops at Minimap#update()).
Nested folded regions problem fixed (d7918de).
Test added.
Put HashSet under the hood of Folds (eaf47b1): much clear logic and code plus better performance.
Fix #218 What actually slowing down minimap refresh was linear search inside
Folds#isFolded()
method (that invoked inside nested loops atMinimap#update()
).