initializes BowlingGame and runs a failing test to check if @rolls is an empty area
adds an attr_accesor :rolls to pass adding rolls to array test
adds and implements test to check that if a bowler got all gutters there score is 0
9: adds a test to check if bowler got 1 pin a round
implements game.score = 20 by using reduce method on @rolls array
11: refactored code to use let(:game)