Fixed image matching regex.
Fixed image matching regex.

".png test".match($.facebox.settings.imageTypesRegexp) would match (incorrect behavior)
".gif test".match($.facebox.settings.imageTypesRegexp) would not match

CantemoInternal/facebox,hagb4rd/facebox,christophercaburog/facebox,rstocker99/facebox,snikch/facebox,hagb4rd/facebox,defunkt/facebox