Fix string contains check in submit function

[westonclark]

Summary

Fix Issue #50

When submitting an answer, the returned message is usually something like "That's not the right answer. If you're stuck, make sure you're using the full input data; there are also some general tips on the about page, or you can ask for hints on the subreddit."

The check if strings.Contains(message, "right answer") was evaluating to true since the string did in fact contain that substring.

Fixed the conditional to be more specific and check exactly for the string "That's the right answer!"

[DaltonSW]

Could've sworn I tested the string checking better but... Can't say I'm surprised. Thanks so much, I really appreciate the contribution @westonclark!

I'll have this in the new release tomorrow morning, but you can run it from source if you're looking to do day 3 at launch