node-discord-bridge is a very barebones but working bridge between Internet Relay Chat and Discord. This project has not been touched in a while, but assuming not much has changed with the Discord API, it should work. If not, a little bit of tinkering could be in order to fix it.
To get started, install the required modules using NPM, then edit config.json. Once you have it configured, you can try it out by running main.js.
Doctor McKay for his "internet-relay-chat" module, which is one of the easiest modules for IRC that I've ever used. No bullshit, just IRC.
izy521 for his "discord.io" module, which is a bit long-winded in its wrapping of the API... but works perfectly for this application in being lightweight, although I haven't paid any attention to it lately so I can't vouch for it still being like this.