Insert a node at the head of a linked list

More practice on May 9, 2016
Linked List on HackerRank:
problem statements:
https://www.hackerrank.com/domains/data-structures/linked-lists/difficulty/all/page/1



Insert a node at the head of a linked list
https://gist.github.com/jianminchen/79dd121f3135769d57088c7d2e9e51fe