Working Softmax Regression
Used sources:
Andrew Ng et. al. UFLDL Tutorial, Softmax Regression. Retrieved from http://ufldl.stanford.edu/tutorial/supervised/SoftmaxRegression/
Sebastian Raschka (2016), Bonus Material-Softmax Regression. Retrieved from https://github.com/rasbt/python-machine-learning-book/blob/master/code/bonus/softmax-regression.ipynb