outorg.el: Fix mode recognition of ess-mode.

* outorg.el (outorg-language-name-assocs): Change assoc (ess . R)
  to (ess-mode . R).
Do not modify original buffer when quitting unmodified edit-buffer.
Update outorg.el
Merge pull request #5 from kidd/patch-1

Update outorg.el
File comment section updated.
File comment-section updated.
New README.md added using ox-gfm.el.
Comment-section and README.md improved.
Copyright years and export template improved.
File old-README.txt renamed to lowercase.
Default export template fixed.