Added test to see if linkedlist contains returns true when querying for a value that exists in the linked list
simple implementation of contains
Implemented addToTail where contains returns correctly
Implemented new test case for contains after two addToTails
passes test for 'contains after two addToTails'
Added test for removeHead
Implemented removeHead, Passes test
removed 'words'
changed test to respect private variables starting with _
refactored to reflect _ naming convention of private variables