Provide visual/interactive examples in documentation

[dcwalk]

We've had multiple requests to add screenshots and more to make the documentation easier to understand, especially for event attendees.

A walkthrough video was created (awesome!) but more could be done!

[dcwalk]

Images from the current interface have been added to:
datarefuge/workflow/tree/master/docs/img

These need to be integrated into the docs (goal for weekend!!)

[dcwalk]

@sharlychan is going to tackle some of these potentially!

I tested out adding some in on #104 , the html I used was
<img src="/img/harvest-00-overview-homepage.png" />

And it seems to work/resize well enough inline. We'll have to do some testing to check tho