added equality test for HLLNode, as nodes must be compared by value and u_id
expanded equality test, as HLLNode must not be equal to any other type, but HLLNode
implementation of equality method, that passes respective test suite for HLLNode
added simple test for __str__ method for HLLNode object
added implementation of __str__ method that passes current test cases
expanded test for hashed linked list to support operation inversion
implemented the "reverse" method that passes current test suite
initial take on implementation of split operation for hashed linked list
added initial tests for hashed linked list to support split operation
added tests for in place split operation, as it otherwise creates a copy of a list, in terms of memory
implemented in_place option for split method of HLList to avoid creation of a list copy in terms of memory. passes current test suite
initial take on tests for merge HLList method
added test to cover the merge method of hashed linked list
introduced merge method of hashed linked list and merge_two_lists static method of HLList
 also added _node_iteration method as a refactoring feature
 commit passes all current test suites