added algorithms
added directory for ROOT macros, and TreeNumpy module
attempt at starting to reorganize gaussian mixture code
added Stack implementation based on list

Not sure about the best way to remove functions from the list interface.
added example for binary tree creation and traversal
dfs inorder recursive working
proper stack implementation (wraps a list)
preorder iterative is working
another version of the inorder iterative algorithm, without the visited flag
added a comment
recursive algo to find nth to last element in linked list
revert linked list