Fix: We should use several test cases here
Merge pull request #98 from matthiasbeyer/fixup-ll_tests

Fix: We should use several test cases here
Added testing file for AVL implementation
Added allocation test for avl test
Added test for testing allocation and deleting for AVL
Added test for adding data to the avl tree
Added test for adding and destroying afterwards
Added test for adding multiple elements
Added test for adding multiple and destroying AVL afterwards
Added test for colliding inserts
Added test for finding a single element
Added test for finding multiple elements