should property already defined Error to include the name of the property

Error exception should include the property name and not `should` (default value).

Just a minor question, I was about to include this change in the PR but probably you did it intentionally:

>      if (this instanceof Chain) {
        // Actually Chain instances don't inherit from Object but still
        return this;
      } else if (this instanceof String || this instanceof Number) {
        return new Chain(this.constructor(this));
      } else if (this instanceof Boolean) {
        return new Chain(this == true);
        // Do you think it's worth it keep like this (we already know this is
        // a Boolean instance), or be "safer" with
        // return new Chain(this.valueOf() === true);
      }