Ask Until Yes Or No

Ask Continue? (y/n) and keep asking, printing Please answer y or n. each time, until the stripped and lower-cased answer (.lower()) is one of y, yes, n or no. Then print Continuing. for a yes and Stopped. for a no. Input: one answer per line; the last line is a valid answer. The prompt is part of the output, so each message follows a prompt on the same line.