Added problem 2 files

Adds ability to print a tree, which happens to be nice when testing
problem 1
Added Node::is_leaf()

Makes it easier to check if a node is a leaf
Added object and exe files to gitignore

Don't want to commit them
Updated scoping, linkage in Amazon_Problem1

Class has no static data; making methods static increases flexibility
Added testing framework and test functions for problem 1

Verifies problem 1 against example
Added problem 2 check

Verified problem 2 against given example