[Linear Regression] Add Following plots

[manashmandal]

• Steps vs cost
• hyperparameters vs cost

Reference

http://stackoverflow.com/questions/28542686/3d-plot-of-the-error-function-in-a-linear-regression http://seaborn.pydata.org/generated/seaborn.kdeplot.html

[manashmandal]

http://www.scipy-lectures.org/intro/matplotlib/matplotlib.html