Add tutorial on regression models (#280)

Summary:
Adding a tutorial on a regression model using Boston House Prices.
Pull Request resolved: #280

Reviewed By: vivekmig

Differential Revision: D20182214

Pulled By: NarineK

fbshipit-source-id: 326e2265d5fc61e2150a05eed9061241d2f9e4a3

Author: NarineK