atbash-cipher: Update test cases (#429)
atbash-cipher: Update test cases (#429)

Adds one missing test case from the canonical test data and
stores the test data version.
exercism/xpython,jmluy/xpython,jmluy/xpython,N-Parsons/exercism-python,pheanex/xpython,exercism/xpython,mweb/python,behrtam/xpython,exercism/python,rootulp/xpython,mweb/python,behrtam/xpython,rootulp/xpython,pheanex/xpython,smalley/python,N-Parsons/exercism-python,exercism/python,smalley/python