Apply Elm Architecture to tidy up Client.js Code a bit?

`while` I am _deliberately_ not using any frameworks/libraries in `client.js` to make it as approachable (_beginner-friendly_) as _possible_ I think the _structure_/_organisation_ of the code could benefit _tremendously_ from the Elm Architecture so it's _clear_ what each piece of the code does and the "flow" of data through the app.

For reference, the `client.js` at the time I am opening this issue looks like this:
https://github.com/nelsonic/time-mvp/blob/994ccf496a3a602fc9e30d0f51690c2792d1b911/lib/client.js
It _works_ but is _rapidly_ approaching "_spaghetti_". (_and **not** the **tasty** kind_!)