isogram: added parameter to template question
isogram: added parameter to template question

I added parameter string to template question
exercism/xpython,mweb/python,N-Parsons/exercism-python,exercism/xpython,smalley/python,pheanex/xpython,pheanex/xpython,jmluy/xpython,exercism/python,behrtam/xpython,exercism/python,smalley/python,jmluy/xpython,behrtam/xpython,mweb/python,N-Parsons/exercism-python