Session03

List_lab homework from session03
Rot13 homework from Session 3
This function brakes if you change the `if...elif` to two separate `if` statements because you're binding the symbol `i` to the shifted string ordinal in line 24 and then using that same symbol in the conditional for the second `if` statement. This means that if `i` is initially a character in the 'lower_half', then it'll be rebound to a character in the 'upper_half' in line 24. The conditional for the second `if` statement is designed to trigger for all 'upper_half' characters, so it'll convert `i` back to its original value.