Change to Node-ish function declaration

Note that I have no idea what I'm doing. Tests still work, though!
Make wrapText less DOM-aware

This will allow us to use it from the CLI with Node.js, for example.
Provide Node CLI version

There is probably a better way to include the node_modules in git, but I don't know what it is. I'm not about to write a deploy script to install node.js and npm underscore (I hope).
Don't blow up on bad input