Thanks, moesasji, I needed that encouragement. ;-)
My head is already lumpy from banging it against all kinds of walls... ;-)
It's now installing which-key...
It's progressing... (I do have 10M/1M ADSL)

It's there. Now I have to find out how it works. I'm familiar with Emacs (although I haven't used it lately) and vi (not so familiar with vim).

Umm...

Why not just make a branch in git, put your README.md update in that branch. Push the branch to github and look at the README.md there. If you like what you see, merge what you did in that branch to the branch that you want to keep and remove the old branch from your local repo and github.

The beauty of spacemacs is that it is pretty well documented and can behave like vim or emacs. Typically you hit "SPC f e h" and search for the thing you need. In these case "markdown". That brings up the needed documentation. In this case hitting ",cp"(short for compile preview) would give the preview as long as you have enabled the markdown layer. Good luck.

coding should be fun, but emacs requires to use defun, so I can not use it

;)

OMG! Emacs has really changed while I wasn't looking... only in about 15 years... :-)
I couldn't even find help - the <meta> seems to have changed. It used to be <esc>...
I'll re-learn later. Now I don't have the time.

I'd just like to see what my Readme looks like when pushed to github before I push it, but it seems to be too hard. Maybe (after pushing next commit) I'll just push the readme and see there...
It just kind of bothers me to use a public site like github for debugging 'simple text'.

Atom seems to work, but even with gfm-grammar selected, it doesn't show stuff the way github gfm documents say. Like ** doesn't seem to make anything bold and ''' doesn't make code block.

[edit]
Aha, gfm examples showed a bit more... Seems to work...
[/edit]

I'm a big fan of Zed. Ctrl + P gets you into preview mode, which renders markdown.

http://slackbuilds.org/apps/zed/

I still use Vim on the console though.

It still is, AFAIK. Note that it's "hit esc" not "press-and-hold esc". If you have a windowsish keyboard, the "windows" key is commonly mapped to meta (as in "press-and-hold" meta).

Help is cntrl-h (as it always has been).

(IMO, if you want to use emacs for this sort of thing, you should look into org-mode to write the documentation in *that* and export into markdown. That is not even close to the problem that you are trying to solve right now. If I were you, I'd use github to look at the markdown; it seems stupid, but the only place that knows how github will render markdown is github itself.)

VIm and Hoedown or Markdown.

What I meant was that <esc>-x didn't get me anywhere. And neither did ctrl-X b or <esc>-b or ctrl-X 1. It looked like <esc><char> sequence were changed to <alt>-<char>.

I selected Emacs Holy, but I found myself using basically Vim (':' brought me to command buffer) and I had to use 'a', 'i' or 'o' to write anything. I checked the dot-file and the settings were consistent with my selections.

I'm checking Atom now. I already edited the file and I'll push and see the results after I've fixed something first. Then I'll see if Atom is good for that.

How the heck can it be so difficult to make a simple viewer... Maybe I'll look into it when I finish my current project - unless there are plenty of simple viewers by then. ;-)

Huh?? Your web browser ain't working for viewing html?
I would not be surprised if Github uses "hoedown" (or a similar tool) to generate the html when displaying the "README.md" file. And "hoedown" correctly converts "```" to "<code>" tags.

Look at:

https://github.com/chenzhiwei/chrome-markdown-editor
https://jbt.github.io/markdown-editor/
https://github.com/jpadilla/ember-poe