Download feature for sample datasets

name: Downloading sample data sets about: Allows user to load in sample datasets from the web labels: feature

This pull request closes #226 .

- What I did allow user to load in data set by specifying the name from the list of our sample data sets - How I did it downloads from our mediafire links - How to verify it

from libra import datasets  
data = datasets.load('housing')

[ ] I updated the docs.

This pull request adds a new feature to libra. @Palashio, could you please take a look at it?

Palashio / libra

Download feature for sample datasets #298

name: Downloading sample data sets about: Allows user to load in sample datasets from the web labels: feature