Send just the latest rows to the browser

[dylanmcreynolds]

When we first set up this project, we were sending jpgs to the browser, so we needed to send all of the current image.

Now we have swapped to sending arrays to the browser, so we can send just the most recent updates rather than the whole array.

Assigning to Dylan but will assign to Seij when there's a branch that sends the new chunks from the server.