Fix incorrect config file name

Author: revolter

docs/automatic_start.md

@@ -5,7 +5,7 @@ Tmux is automatically started after the computer/server is turned on.
 ### OS X
 
 To enable this feature:
-- put `set -g @continuum-boot 'on'` in `tmux.conf`
+- put `set -g @continuum-boot 'on'` in `.tmux.conf`
 - reload tmux config with this shell command: `$ tmux source-file ~/.tmux.conf`
 
 Next time the computer is started:
@@ -39,6 +39,6 @@ Help with this would be greatly appreciated. Please get in touch.
 ##### this will only start the tmux server, it will *not* start any terminal emulator
 
 To enable automatic start with systemd:
-- Put `set -g @continuum-boot 'on'` in tmux.conf
+- Put `set -g @continuum-boot 'on'` in `.tmux.conf`
 - reload tmux config with this shell command: `$ tmux source-file ~/.tmux.conf`
 - see [systemd](./systemd_details.md) for more details about how this is implemented