ANSI escape characters not rendering correctly

See #56 for more context.

As @dzop requested, here's some additional debugging output.

In an org-mode buffer I ran eval-expression and ran:

(with-temp-buffer
  (org-mode)
  (insert ": �[31mhello�[39m")
  (font-lock-ensure)
  (text-properties-at 8))

which returned

(face org-code wrap-prefix "" line-prefix "")

I created an elisp file (with the proper escape character which isn't displayed here):

(push "~/.emacs.d/elpa/26.3/develop/jupyter-20190917.1642" load-path)
(push "~/.emacs.d/elpa/26.3/develop/simple-httpd-20190110.1505" load-path)
(push "~/.emacs.d/elpa/26.3/develop/websocket-20190621.54" load-path)
(push "~/.emacs.d/elpa/26.3/develop/org-plus-contrib-20190909" load-path)
(require 'org)
(require 'jupyter-org-client)
(with-temp-buffer
  (org-mode)
  (insert ": hello")
  (font-lock-ensure)
  (prin1 (text-properties-at 8)))

And ran it with emacs -Q -batch -l /tmp/ansi-test.el. emacs exited with status 0 but otherwise didn't produce any output.