In the Mineflayer wrapper, server should shutdown when the bot disconnects. #91

For bot examples like the reconnector bot, which simply creates a new Mineflayer instance or larger applications that manage many bots at once, keeping a server socket live long after the bot disconnects can have adverse effects and eat up performance and memory. by default, the wrapper should listen for the 'end' event and shutdown. I imagine this can be shut off in the startup options, but it should not be the default behavior.