Adding secret number homework (9/22)

Pull request of homework for BEWD 13. Secret Number Game.
Love the additional styling of the command line output. One thought to make this DRY (dont repeat yourself), you could create a method that creates these divider lines for you.
It might look like
```def create_linebreak
puts "======================================"
end```
The added benefit of that is that if you need to change the length of the linebreak, you only have to change it one place .