Conducts an iterated prisoner's dilemma. The goal is to determine
whether altruism is a natural biproduct of self-interest. Specifically,
if you have the opportunity to help someone else at some small
cost to yourself, will doing so benefit you in the long run?

In this version there are four algorithms:

Generous always cooperates
Unhelpful always defects
TifForTat coperates on the first play and afterward copies the other
   player's choices
BigGrudge cooperates until the other player defects. After that it
   always defects

Output after each matchup between algorithms is displayed in a terminal
window.
adding .gitignore
Merge https://github.com/Spiffer1/PrisonersDilemma

Accidentally added a .gitignore separately to the gitHub repo and the
local copy.