added node, heap and tests classes
added tests for node
added "Add" method for heap
used int as key type
added 'merge' and 'extractMin' methods
fix style and copyPaste
fixed style and mistakes
fix style
added gradle
added extractByKey and decreaseKey methods
refactoring
refactoring
remove comments
added test and refactoring
fix using of key instead dist
using assertArrayEquals and added check for null to merge method
fixed style and mistakes
added gradle
added extractByKey and decreaseKey methods
refactoring and clear code
added test and refactoring