Add aria tags to generated svgs

[barlock]

SVGS could use an aria-labeled-by="title" with a title for better accessibility on screen readers.

[seejamescode]

Yeah, I just read this article about accessible SVGs. It seems like our responsibility in this code is to add <title></title> inside of built SVGs.

It also sounds like we should recommend the use of aria-label and aria-hidden for their appropriate purposes in the Readme. Agreed?