--remove not triggered when peerflix exits because player was closed

[jrouleau]

-r, --remove remove files on exit

When --remove is set, files should be removed regardless of how we exit.

Currently, engine.remove() is only triggered on SIGINT and SIGTERM and not when we exit after the player closes as we are directly calling process.exit(0) from the [player].on('exit') callbacks.

[mafintosh]

Yea that's a bug. Wanna pr?

[smallbrownbike]

Pending pr