Modularized Puppy Class.

Made the @@list(database of puppy info) as a new instance of PuppyRepo
Passed all the tests in puppy_spec.rb
Added comments to each funciton in both puppy.rb and breed.rb.
Forgot to mention that I added some test parameters to puppy_spec.rb: check for non-existing breeds and update quantity. Once again, all test passed succesfully.