Tally the words in a text

Here is a task you have almost certainly done by hand: go through a text and count how often each word appears. On paper you add a gate mark under each word and count the marks at the end — slow, and one missed mark spoils the count. This is the capstone of the discipline: everything you have learned, turned on a real job. This first module does the word tally — a loop and a dictionary, working together.