Add Linear Algebra Examples to Vectorized math section

[rsokl]

Now that the section on vectorized operations doesn't suck, it'd be good to add a few simple examples of linear algebra functions. The subsection already exists.

I'm thinking dot products, matrix multiplication, and maybe a simple example of einsum.

[davidmascharka]

Would you want to cover any of np.linalg? I know things like norm can come in handy, but that might be outside the scope of the site/available for people that read the docs.

[rsokl]

Yeah, I think that is a good idea. Maybe norm and inv, to indicate the wide variety of functions available.

[AFederici]

For norm you could probably present a euclidean distance problem as an example of its utility. I remember for last year it is what I used to do the distance calculations in my Nearest Neighbor program.