Polished your README!

[NuclearMachine]

Hey Shopify, thought your README could use some help!

I added a getting started section and formatted most of the readme so that it's easier on the eyes. I also added a quick video demonstrating the new getting started section. It's hosted on replayable.io, a company that's sponsoring my contributions.

If you accept my PR. We'll have our bot check your readme everyday for changes and notify us in case we need to update the instructions (or the video I've added). We respond to changes real quick (usually within a day or two).

Let me know what you think or if you have any questions.

I believe these changes will help your users especially newbies who might be looking to use your library.