Solve the active learning problem from our last meeting:
Write a function called rot13 that uses the Caesar cipher to encrypt a
message. The Caesar cipher works like a substitution cipher but each character
is replaced by the character 13 characters to ‘its right’ in the alphabet.
So for example the letter a becomes the letter n. If a letter is past the
middle of the alphabet then the counting wraps around to the letter a again,
so n becomes a, o becomes b and so on. Hint: Whenever you talk about things
wrapping around its a good idea to think of modulo arithmetic.