Create treetraversal.py

file contains inorder,pre,post,level,spiral  level order traversals.Building Mirror tree.Functions to find height,size,depth,diameter of the tree.Function to check identical tree,getting all paths in the tree,whether the give number exists in the path sum ,getting leaves count,whether the tree satisfies child sum property,tree is height balanced or not,find maxwidth in the tree,check whether the tree is foldable or not,finding k distant nodes in the tree.