Trying to Add a Specific Menu Depending on User Group
OK, so enabling the devMode helped point me in the right direction.  

First, I needed to change it to 

{% if currentUser and currentUser.isInGroup('advisors') %}


Otherwise I was getting an error message when nobody was logged in ("Impossible to invoke a method ("isInGroup") on a null variable").

Then I discovered that the user I was testing wasn't added to any groups!  I could have sworn I set up the user with a group assigned, but apparently not.  :(