You need to tell the bosses that because you just saved the company mucho moolah by doing this haphazardly, you deserve a raise; otherwise you no longer feel comfortable supporting the code since that's really not your job. Sure, it works *now*, but later you can't really expect. Who knows what bugs crept in when you weren't looking--after all, this is way above your pay grade.
Also, look into being able to write off your personal time/equipment on your taxes, since that's where the development was taking place. Additionally, see if FLSA kicks in, since you pretty much volunteered time/effort to the company without compensation.