gnu: emacs-ess: Update to 17.11.

* gnu/packages/emacs.scm (emacs-ess): Update to 17.11
[url]: Use github for https
[snippet]: update julia-mode substitution, only build info doc, bypass failing test
[propagated-inputs]: Add emacs-julia-mode
[description]: Mention that ESS supports Julia and JAGS (which replaces OpenBUGS)
[arguments]: Remove 'set-home' phase.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>