Implement ALS and MCMC

[Hydrotoast]

Implement ALS/MCMC similar to libfm and fastFM. This training method does not require a learning rate alpha. Both libfm and fastFM reuses a single class for both training methods due to common code.

For reference:

• libfm implementation
• fastFM implementation

I have implemented the ALS algorithm in the past; however, I have not implemented an MCMC implementation before. I would proceed by first implementing the ALS algorithm and then attempt to implement the MCMC algorithm.