Recursive-sgd

In this release, several useful features were added such as ReLU activation and batch shuffling

Fix of math bugs, after discovering error in convergence. The bugs were discovered almost by accident, but were sucessfully anihilated with the help of two separate ML blogs.

First release which converges sucessfully.

Activation functions:
- Sigmoid
- TODO:
- ReLU, Tanh, ...

Loss functions:
- Mean Squared Error
- TODO:
- Cross Entropy