Minor (but IMO critical) language update in documentation

[tblancher]

tl;dr

Changed the language of the README.md and docs/automatic_start.md: tmux-continuum does NOT restore the tmux session on computer boot, but on user login, as far as I can tell, for both macOS and Linux.

Longer explanation

I finally reread the tmux-resurrect README.md, and I saw mention of this tmux-continuum package. I was highly intrigued, since several months ago I hacked together a goofy way to start tmux on login.

Ultimately I got it working nicely, but it was a really kludgy hack. Today I decided to break it to try and make it "better," and broke it all over again. I think I ran into the same problem as before; namely, tmux-resurrect starts so fast, that every zsh in my saved sessions seems to try and launch itself again; it seems there's some kind of race condition and each zsh session tries to tmux new-session -As ... and I get the dreaded "sessions should be nested with care, unset $TMUX to force," which shouldn't be happening since I'm testing for the existence of ${TMUX} and only trying to create/attach to the session only if it doesn't exist.

After reading the tmux-continuum README.md I was disheartened, since it says once enabled, starts itself on computer boot. This is actually what I don't want. Actually, in my case (at least on Linux), I'm running systemd-homed, so it really can't start on computer boot.

When I started reading how this works, I discovered it's actually exactly what I want, at least on Linux, since it uses the systemd user mode. It looks the same on macOS, but there a few reasons why I won't try that there yet. Namely, my setup there is a lot more stable than Linux (since I have to use it for work), and my setup is pretty stable there already. The other reason is I don't have admin/root access to that machine (I can get it with an IT helpdesk request, but only for five minutes, and it's always a pain to request it so I'd rather not). I also hate launchd plists with a passion (XML is worse than YAML as a config file format, but they're both really effin' bad).

I actually haven't tried tmux-continuum yet, but I thought the language saying it started on computer boot is factually incorrect, and what are we nerds if not pedantic?

[tblancher]

Just fixed one of my filename mentions which was supposed to be in italics. The underscore _ delimiter for italics needs to be greedy, but every Markdown system I've used seems to treat it as non-greedy. It always seems to break when the sting to be italicized also has underscores in it. At least GitHub's Markdown engine provides an alternative with single asterisks *. Slack's, unfortunately, does not.