Merge pull request #9 from s1monw1/upgrade_sample_app

Upgrade sample app to 0.0.9

Fix bintray upload

re-wrote tests to run on junit 5 jupiter; created custom exception ty…

…pe which is thrown for script loading errors; added feature to provide custom classloader to script loading

changed engine to instance variable, documented thread-safety; change…

…d kotlin version

new version with renamed packages

introduced new API functions

merged from origin

fixed engine access