Clean up the RevBayes setup tutorial

[davidcerny]

This PR makes several changes to the "Setting Up RevBayes" tutorial inspired by discussion #712:

• The test.Rev script no longer ends with the q() command, which closes the program window on Windows and makes it impossible for the user to see if the script was successfully executed;
• We no longer use braces ({}) in the instructions on how to specify the path to the RevBayes executable in Revticulate, because they could confuse the user into thinking the actual path should be enclosed in them.

As I was making these changes, I found a few other problems – e.g., the actual output of the script didn't match what was shown in the markdown, and the text kept referring to a data file called primates_and_galeopterus_cytb.nex, which was not provided. I have fixed these as well, along with a few typos.

[brpetrucci]

Looks good! I think it would be better if you could use the snippet commands to pull code directly from the script, and in that way we can ensure the script and tutorial always agree. But this is a unique kind of tutorial I guess, so I don't think that's necessary