Adding Gale-Shapley Algorithm to solve Stable Matching/Marriage problem

[HarrisonL7]

This is a(n):

• New algorithm
• Update to an existing algorithm
• Error
• Proposal to the Repository

Details:

Given n men and n women, where each person has ranked each person of the opposite sex according to their preference. Males and females are matched such that there are no two people of opposite sex who would both rather have each other than their current partners.

I have not found this algorithm in this repo, not sure if it is under another name. I will provide a Java Implementation. Let me know if it should be called gale_shapely, stable_marriage or stable_matching.