I have added a more detailed tutorial on IO(). I feel that what was there before would only make a newcomer confused. When I was learning this, the crucial insight was to understand how to interpret the types of the IO functions, and I tried to elucidate this.
There are also three minor, related changes:
I changed the `say` function to be Color -> String. I found the older version Color -> IO String confusing, and it did not compile anyway. I also use the new `say` function.
I added a note that the REPL can run IO actions.
There was a minor error in the `action` function that I fixed.
Since all the functions work with lists, calling them arrays is inaccurate. This commit also updates `myMap` function so that it works on an empty list as well as resolves ambiguity about `x` from comment.
