Fix bugs when $EDITOR="emacs -nw"

This patch fixes 2 problems at once in the default config, which prevent one
from editing files when his $EDITOR variable is set to "emacs -nw":
- $EDITOR variables consisting of "program name + options" are not handled
  correctly because of quotes around $EDITOR. As a result, if $EDITOR is not
  a simple program name (i.e. if it includes options, as in "emacs -nw"), the
  full string is taken as a program and fails to run.
  Error message: (/bin/sh: 1: emacs -nw: not found)
  Removing quotes fixes this problem.
- emacs does not seems to handle the "--" correctly: it does not open any file
  when it is there. I don't know why it is there, but removing it does not
  prevent other editors (vim, nano) to run correctly, and makes emacs work.