begin functional example
pass first test with trivial implementation

same as declarative example
set up data structures for calculation

One array to hold all of the frames and one array for the rolls in the current frame
helper function to determine if a frame is complete
add rolls to current frame and store completed frames
sum up all of the rolls

uses many of the `Enumerable` methods.

Now the first two tests pass.
use `attr_reader` to simplify code

Effectively creates a temporary copy of the variable to allow for arbitrary manipulation without affecting the actual values.
begin introducing constants
refactor to compute score for each frame individually
compute score for spare
add score computation for strike

passes test 4
special case for final frame

passes all tests
Complete Functional example