Added Nick Becker's Testing 1, 2, 3 Assignment

Adding 3 test file for the "Testing" assignment. Will add the test_html_render when I have the final word on what exactly is needed. 
These tests are properly written and sufficient. However, they will not run via `py.test` due to the interactive code in ROT13.py. Tests are another reason to keep interactive code inside an `if __name__ == "__main__"` block. Since Pytest prints an error message, "E   IOError: reading from stdin while output is captured", in red it indicates that the tests weren't themselves tested.