non-kubeadm mode has been removed since ddffdb63
2.5 years ago. The non-kubeadm makes unnecessary confusion today, then
this updates the documentation.

When https://kubespray.io/#/docs/comparisons is generated, having the link in the heading creates the following HTML. When displayed there is no space between "vs" and the link. I simply moved the link into the following paragraph.

```
<h2 id="kubespray-vs-kops"><a href="#/docs/comparisons?id=kubespray-vs-kops" data-id="kubespray-vs-kops" class="anchor"><span>Kubespray vs </span></a><a href="https://github.com/kubernetes/kops" target="_blank" rel="noopener">Kops</a></h2>
```

Although it is spelling mistakes, it might make affect while reading.

Signed-off-by: Nguyen Hai Truong <truongnh@vn.fujitsu.com>

Minor grammar fixes

Link docs to README, update README with recent info.
Update comparsions, add kubeadm vs kargo.
Better describe variables precedence UX impact.

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>