Wrap output of `exercism debug` in markdown Codeblock ready to paste

We often ask to copy and paste the output of `exercism debug` into the gitter, some GitHub issue or the slack.

This requires students to actually know about fenced code blocks or other means of wrapping stuff before posting. Not properly wrapped output often gets reinterpreted and formatted by the rendered of the service we paste into. This often makes the output hard to read.

Therefore I suggest wrapping the output in a fenced code block making it look like this:

`````md
```
... Exercism debug output ...
```
`````

This will be colorful when posting to GitHub as it will try to guess a language on its own and probably will not pick "plain", but gitter and slack both don't support specifying the language on the opening fence, therefore I consider this the greatest common denominator to choose from.

Downside of this is, when a student misses to copy either opening or closing fence or even a single backtick, it might blow up the complete post of that user when writing something large in GitHub.