Bumped version for release

Release/0.4.0 (#37)

* Feature/dft refactor (#36)

* Initial refactoring

* Removed used PaintTool class

* Layer rendering

* Improvements

* Fixed imagelayer render algorithm

* Bug fixes

* Improvements

* Added GraphicsContext

* Checkpoint

* Improved tool builder; package refactoring

* Reverted introduction of delegate pattern

* Added configurable properties to ants

* Improvements to filltransform

* Refactored builder inner classes

* Eliminated surfaceInteractionObserver template method

* Added AirbrushToolTest

* Added FillToolTest

* Airbrush tool behavior improvements

* Enabling JUnit5 tests

* Fix for headless test failure

* Fixing Optional issues

* Enabled Jacoco

* README and transfer handler improvements

* Readme fixes

* More README updates

* Added tests

* ImageLayerTest

* Completed test for ImageLayer

* Improved test method names

* Refactored structure of tools

* Added BasicToolTest

* Added BoundsToolTest

* Improving BoundsTool test coverage

* Improved parameter name in SurfaceInteractionObserver

* Added LinearTool test

* Fixing Sonar bugs

* Enabling Sonar branches

* Added PathToolTest

* #35: Fixed polyline issue

* Readme updates and refactoring

* Deleted tester

* Javadoc fixes

Feature/transform refactor (#33)

* Refactored transforms

* Code cleanups

* Bumping version

Bumped version for release; minor API improvements

Bumping version for release

Improving default scanline color

#26 Correcting issue with unmodified selection

#25 Correcting rotate animation issue

Bumping version for release

Bumping version for release