Implement getting user input function

[samdai01]

Purpose

The user will enter commands for what data or test or menu they want to view. We need to parse their input into a string and return it to the app for processing

Description

Until the user inputs a series of alphanumeric characters, reprompt for input
Need to account for the case where the user inputs any symbol other than lowercase letters and numbers -> in this case try again
Once we obtain proper input, parse it into a string and return it