Website and repo docs updates

[geerlingguy]

Along with some of the other changes I've recently made, I need to do a little work revamping the website a bit. Some of the subtasks:

• [ ] Consider switching the theme to be a Bootstrap subtheme. But maybe no LESS/SASS just for simplicity's sake.
• [ ] Take some new photos, get a new 'hero' shot with the PoE switch and four nodes (or heck, maybe set up the 5th node as a battery-powered load balancer in front of the cluster?? That could be cool, and could even proxy/cache so you could have content even when the cluster is down).
• [ ] Maybe make the logo a bit larger?
• [ ] Change mentions of 5 or 6 nodes to 4 Pis default, with the ability to easily scale to 200+ Pis.
• [ ] Change any mentions of the full cluster specs (in README and elsewhere) to adapt it to 4 Pis as the baseline.

[geerlingguy]

I've done a number of these things, and will complete the rest, in the new Drupal Example for Kubernetes repo: https://github.com/geerlingguy/drupal-for-kubernetes/issues/9