Implement module Battle

Describe module Battle separately
Move API host and exception classes to module Battle
Later can easily require only one file which will able
to require all needed files of the library
Implement Ship class

Ship can be created by name and asks by name is
it this ship or not
Ships set

Stores set of ships after game inialization
This will able to count how many ships left at the battlefield
Move game URL's into module

Move register and nuke urls into Battle module
Sink the ships

Sink the ship if it's got destroyed. Decrease game ships count.
When game reach zero ships win the game
Refactoring Game class

encapsulate bunch of code from register! and nuke methods
sets coordinates from nuke response
rename 'lost' status to 'defeat'
Extract Battle into gem

lib/battle was extracted into separate gem 'battle'
Gem's source code are on GitHub https://github.com/ck3g/battle