Testing Game and Guess objects

Testing game initializer; word is selected from dictionary, letters are selected from word
Testing guess credentials; player inputs guess, player gets incorrect guess, player gets correct guess
Typically we'll structure our tests like this:

```ruby
describe Game do
  describe ".a_class_method" do
    ...
  end

  describe "#an_instance_method" do
    it "does something fancy" do
    end
 
    it "does something else fancy" do
    end
  end
end
```

So, for each public method in the class, there will be a describe block. `#` for instance methods. `.` for class methods.