Return the result of merging these arguments.
TODO: What happens when we're merging arguments for the single string
case and some of the arguments are in quotation marks?
function(following) {
        if (following.emitter != this.emitter) {
            throw new Error('Can\'t merge Arguments from different EventEmitters');
        }
        return new Argument(
            this.emitter,
            this.text + this.suffix + following.prefix + following.text,
            this.start, following.end,
            this.prefix,
            following.suffix);
    }