If launching Emacs from outside an interactive shell (say from Upstart,
Gnome3, an OS X .app bundle), $TMUX and $STY won't be set. We shouldn't
launch ssh/tmux when running emacs, because emacs can't handle the
termcaps of such multiplexers.
Emacs sets $INSIDE_EMACS and (on older versions) $EMACS, so if those are
set we won't attempt to autostart a tmux/screen session.
Setting the auto-start 'remote' and 'local' zstyles for the screen and
tmux modules to 'true' automatically starts a session in SSH connections
and in local terminals respectively.
Signed-off-by: Sorin Ionescu <sorin.ionescu@gmail.com>
