Add node module support

[AlMcKinlay]

It would be great to allow pory bot to pull in commands from node modules.

This would allow us to more easily add commands that aren't going to be pushed into the core repository, and if you put something in that isn't published on npm it would even allow you to put secret commands that no one knows about, if anyone ever wanted to do that on a published version of pory bot. Would also allow us to pull out the reddit specific stuff and maybe turn this into a fully configurable bot more useful for more people.