Change "Interrupt again" message

Everyone I've ever paired with is trained to mash ^C again and again until they get the prompt back.

When you hit ^C Rspec says "Interrupt again to exit immediately". This seems to indicate that you *should* interrupt again, so everyone I've ever paired with just keeps mashing ^C at this point. But if you just wait a *second* longer, RSpec will kindly show you the report of specs run up til now. This is a great feature and more people should use it!

This patch updates the message to indicate what great rewards await if you *don't* interrupt.
Merge pull request #1742 from rspec/change_quit_message

Change "Interrupt again" message