Release v0.4.0

fix memory leak in builders: they should not hold on to the original …

…collection (#193)

Improve ImmutableMapTest.noOperation test

Upgrade infra plugin version to 0.4.0-dev-80

Add other Darwin K/N targets

Update README.md for 0.3.4 release

Workaround for Bintray treating .sha512 files as artifacts

Update kotlin version to 1.3.71

Update kotlin version to 1.3.70

Update readme for 0.3 version