Catch SIGTERM signal to gracefully terminate

[pataquets]

While dockerizing the app, I've found that it ignores SIGTERM signals from both CTRL+C and docker stop commands (it just gets killed after 10 seconds in the later case).
Trapping SIGTERM signal to terminate gracefully would prevent this annoyance.
Thank you for this useful app.

[hgoebl]

I tried to manage this, but without success. Seams like Socket.IO is a bit nasty when an immediate shutdown is desired. If you want, you can try with branch https://github.com/hgoebl/nerdshow/tree/0.5.0-sigterm-and-upgrade-dep and create PR then. Don't have enough time currently.

[pataquets]

Tested it and works OK, thank you.
Successfully viewed "About" demo slideshow and used remote without problem.
Excerpt from stdout:

Starting src_app_1
Attaching to src_app_1
app_1  | No argument given for folder - taking examples...
app_1  | Express serving `nerdshow` at http://localhost:8008/
app_1  | Process ID: 1
app_1  | Serving files in /usr/src/app/examples
app_1  | Socket connected! id: IJLvPL_ENvRnqJFdAAAA
app_1  | Socket connected! id: n7IyzoaLD_eRuFBsAAAB
app_1  | SIGTERM received, shutting down...
app_1  | express closed
app_1  | io closed
src_app_1 exited with code 0

PR sent as instructed.

[hgoebl]

Thanks for contributing @pataquets
npm published minutes ago.