Session03 Task 1 List Lab and Task 2 Rot13

Create session03 folder, List_lab.py, and Rot13.py 
Consider adding the characters to a list and using `str.join()` to produce the final string. "It's faster, uses less memory, and you'll see it everywhere anyway." --[Jeff Knupp](https://www.jeffknupp.com/writing-idiomatic-python-ebook/)