Create a function that takes a number and returns its multiplicative persistence, which is the number of times you must multiply the digits in num until you reach a single digit.
bugger(39) ➞ 3
// Because 3 * 9 = 27, 2 * 7 = 14, 1 * 4 = 4 and 4 has only one digit.
bugger(999) ➞ 4
// Because 9 * 9 * 9 = 729, 7 * 2 * 9 = 126, 1 * 2 * 6 = 12, and finally 1 * 2 = 2.
bugger(4) ➞ 0
// Because 4 is already a one-digit number.
N/A