Standard Normal Distribution CDF

This program calculates the cummulative area under the standard normal curve for a given z-score. This is denoted by P(Z<=z). The approach for the numerical integratioon of the solution can be found at Numerical Approximation of the Standard Normal Cumulative Distribution. Please refer to this document to how the probabilities are calculated. The code is similiar to that of the c-code given, and the algorithm in theory is identical.