[ESS] ESS from MELPA, but no ess-mode major mode unless *R* buffer exists

[Joseph Mingrone]

Hello,

Until recently I installed ESS through the FreeBSD ports system.  When I
opened an R file, the buffer would have the major mode ess-mode.

I've uninstalled the FreeBSD ESS port and installed the ESS package from
MELPA.  Now I don't see any ESS functions available and when I open an R
file, it's started in fundamental mode.  If I have an *R* buffer/process
opened before I open the R file, things work as they did before.  Can I
get the old behaviour back?

Thanks,

Joseph