Problem
Write a program that scrapes the text of all Python exercises on codingbat. The program should start, identify the links for all exercise categories (e.g. Warmup-1, String-1, etc.) and follow these links. On the page of every category, it should then identify and follow the links to the exercises (e.g. string_times, front_times), and scrape the text for every exercise. Finally, it should store the text of all exercises in a single csv file called codingbat.csv.