Torts — Negligence — Attorney’s fees — Offer of judgment — Judgment which exceeded more than 25% of offer only when award of punitive damages was taken into account — Error to find that plaintiff was entitled to recover attorney’s fees and investigative costs pursuant to section 768.79 where plaintiff had yet to add a punitive damages claim to complaint at the time offer of judgment was made, and offer explicitly disclaimed punitive damages — Offers of judgment must be evaluated as of the time of the offer and must be as specific as possible, leaving no ambiguities so that the recipient can fully evaluate its terms and conditions