add in queues exercises and tests
add linked lists exercises and tests
add singly linked list, complete exercise, and clean up tests
Merge branch 'linkedlists' into queues
update singly LL constructor for use as fundamental data store for queue
refactor to use a singly linked list as core data store structure and write tests for same
Merge pull request #2 from GabeMedrash/queues

add in queues exercises and tests