Added singly linked list implementation of Queue.
Added singly linked list implementation of Stack.
Merge pull request #1 from mfrancis95/ross
peek() no longer throws NullPointerException when it's empty.
peek() uses ternary if statement. Removed unnecessary private modifiers to Node's members.
Merge pull request #2 from mfrancis95/mike

Minor LinkedQueue and LinkedStack changes
Merge branch 'master' into ross