Logistic Regression

**Reported by sumedhghaisas on 12 Oct 43750599 09:03 UTC**
Implementation Of Logistic Regression with l2-regularization

Files -
logistic_regression.hpp
logistic_regression_impl.hpp
logistic_regression_function.hpp
logistic_regression_function_impl.hpp

Implemented a regression class which takes optimizer as a template and implemented methods to support both L_BFGS and SGD optimization. 
