Add helpful information to the SETUP.md

[kytrinyx]

The contents of the SETUP.md file gets included in
the README.md that gets delivered when a user runs the exercism fetch
command from their terminal.

At the very minimum, it should contain a link to the relevant
language-specific documentation on
help.exercism.io.

It would also be useful to explain in a generic way how to run the tests.
Remember that this file will be included with all the problems, so it gets
confusing if we refer to specific problems or files.

Some languages have very particular needs in terms of the solution: nested
directories, specific files, etc. If this is the case here, then it would be
useful to explain what is expected.

---

Thanks, @tejasbubane for suggesting that we add this documentation everywhere.
See exercism.io#2198.

[rebelwarrior]

The setup for R doesn't work. There is no run_tests utilities.

[kytrinyx]

@jonboiser would you have time to look at this?

[rebelwarrior]

I did some digging and the issue is that run_utilities is a separate file that's included with hello world but not word-count. This seems like a complicated setup. And the information on how to set it up is on the hello world readme. That information (with more detail) should reside in the setup file.

[rebelwarrior]

I found the error and submitted a pull request. It was on TEST.md. There was a reference to "run_tests" that seems to be a different way of running the tests. The way it should say is Rscript <testfile>

[jonboiser]

@rebelwarrior Thanks for pointing this out. I forgot to update TEST.md when I was simplifying the problem folders to just have a few files.

I updated the TEST.md with the updated info and did a scan through all the docs to see if there was any more contradicting info.