implemented multiple ships in battleship

- added prompt for number of ships.
- makeship() makes as many ships as specified by num_ships, the first one being size ship_size and each following ship being previous size - 1. It does this by randomly generating ships and checking if they overlap until they fit properly.
- added parentheses around strings
Merge pull request #1 from GriffHub/patch-1

implemented multiple ships in battleship