Does not exit on SIGINT if web client is connected

[wchill]

Expected Behavior

Bot exits when SIGINT is fired.

Actual Behavior

Exiting PokemonGo Bot is printed but nothing happens until all clients connected to the web server plugin exit.

Steps to Reproduce

• After the web plugin is loaded, open up the webview in a browser
• Without closing browser, send SIGINT with Ctrl+C or some other method

Can probably be fixed by firing an event when the bot is going to shut down, allowing plugins to clean up their state. Alternatively, force the program to exit by installing a SIGINT handler.